San Carlos is a great little dive destination for Arizona divers. It is about 6 to 8 hour drive from Phoenix. 4 hours from the border. The drive is pretty straight and two lane highway except through Hermosillo. Just follow the signs to Guaymas and you will be fine driving through the city.
From the border you will need to cross through customs. Pretty easy: Green light, proceed without stopping. Red light and pull over to the customs folks. My advise is to not speak any spanish. If you do, they will try to engage you and keep you there. If you don't, they will look through your car/truck and you will quickly be on your way. Remember, with Mexico, you don't want any weapons (including shell casings), drugs or anything else that could be considered trouble.
After crossing through the first border check, you will come to a toll booth. Give them a US $20 bill. They will give you change in Pesos. The cost is $37 Pesos or roughly $3.70 US. You will almost immediately go through another Red?Green Checkpoint. About 10% of the travelers get pulled over here.
After this checkpoint, you will head to CLICK21 which is about 15 minutes from the checkpoint. It is a big white building complex. You will need to stop in here and the driver will need to bring his/her passport and get a 4 or 7 day tourist visa. There is no cost and a lot of folks will tell you that you do not need to stop. It only takes about 5 minutes and believe me. You need it. At CLICK21 you will pass through another red/green light checkpoint. After this, you are a straight shot to the next toll booth. It is about 1 hour down the highway. The toll is 19 Pesos. You should have change from the first toll. Pay your toll. If needed, this is a good place to go to the bathroom. As soon as you park, a bunch of kids will attack your car to clean the windows. If you want them too, let them. If you don't wave them off and say no gracias. Be careful if you let them, as they sometimes need to jump on your hood to wash the window or will scratch your fender with their belt buckle. They work cheap. Once done here, you will proceed another 90 minutes down the road to the next (last) toll booth. This is 59 Pesos. Again, another good place to stop and go to the bathroom although the area was under construction last month.
Hermosillo is about 10 minutes away. You will take a left at an intersection where there is an old (abandoned) GM dealership. You will see the Guaymas sign pointing left. Stay on the main road. You will wind through the city, take a left which will bring you along a dam on the left hand side. Then a prison on the right hand side. Here you will want to follow the signs carefully to Guaymas. You will merge right then left. After the merge towards the left you will see a KFC Restaurant on the left. At this intersection (between the yellow hotel and KFC) you will turn left. This intersection is also well known for window washers.
After this left it is about an hour to an hour and half "straight shot" ride into San Carlos.
As you enter San Carlos, watch your speed. You will have radar traps all along the road into San Carlos.
San Carlos is a quaint little diving and fishing town. However, it is growing up fast and you will see that with all the condo development and construction. Diving and Fishing are the main things to do. Shopping and beach are secondary and not overly available. The best beach is Algodonis Beach. A great point to access that beach is at the Soggy Peso on the far North side of town. A great little beach bar. I highly recommend it. You can rent jet-ski's, ATVs, and kayaks. Much like Cabo San Lucas, just not as glitzy. I also hear there are some decent hiking trails up Tetakawi, the signature landscape marking of San Carlos. Guaymas is about 20 minutes away and it is a bigger city with more shopping and a dolphin experience. I have never found much reason to go to Guaymas. If I wanted a walmart and mcdonalds, I would have stayed in Phoenix.
The best hotels are the Marina Terra and the San Carlos Plaza. There are good and bad home and condo rentals available in the town as well.
My choice for restaurants (in order of preference): Toro's (Try something different with the Mortar Bowls), Fiesta Real (a little pricey), Joey's Bistro (for Italian), Tequila's (always on the first night), Jax Snax for lunch (great burgers and pizza), Marina Cantina (great sandwiches after diving - try the Yacht Club), the Soggy Pesa (outstanding salsa (more of a snack than a meal). Rosa's has a great breakfast and Evies is great for a quick coffees (across the street from the Marina Terra)
Algodonis Beach is great for sunsets.
Diving in San Carlos is always best from a boat. There are several Dive Charters down there. I imagine they are pretty booked up for that weekend already. Oasis Divers is located in the Marina and has access to several boats. Gary's is one of the oldest and has six boats. Ocean Sports is located in the Marine. The Nomad is a last option. Slow and hard to get a hold of. El Mar has a new boat. If you haven't made your arrangements yet. I would suggest doing so. Oasis and Ocean Sports are who I use. (Full Disclosure - I used to be affiliated with Oasis).
Diving from a boat, you have two options. The first option is local diving. That is usually where you end up if you are on an afternoon boat. There are some great options locally and some poor options. If conditions are wavey and windy, you will end up diving locally no matter what time of day it is. Good local sites include Window Rock, Seamount (my favorite) and the Aquarium. I don't like Martini Cove unless the boat can tuck us into Catalina. If conditions warrant and you are on a morning boat, you will head out to the highway. The water is always a little cooler (2 degrees) out there but the visibility is better. There are many great sights. My favorites are North Point, Roca Grande, South Point and Lighthouse. If the conditions are really favorable, I enjoy the ferryboat wreck. However, it is in 60 feet of water and the area is unprotected, so it has to be flat-flat for most boats to stop there. Also, if there are any new ow divers, most operators will not head there because of the depth and currents.
The other option is shore diving. Lalo's cove is the best place to do that. Algodonis is too Sandy. When Diving Lalo's, stay to the right; that's where most of the rock structure is and where you will find the best marine life.
You can expect to see a lot of reef fish (sgt major's, damselfish, yellowtail, porcupine fish, moray eels, etc.). Hopefully, you will have the chance to dive with some sea lions. They give birth in May, June and July. So if you see some small pups, they can be a ton of fun. Very playful. Listen to the Sea Lion briefing about the 'big daddy's'.
I always recommend DAN or other dive insurance. I also recommend getting Mexican Auto Insurance. Don Smith's has always been a good value. You can buy that online before you go and save time in Nogales.
Leave a copy of all your credit cards, passport and other important documentation with someone at home. If you lose this, it can be faxed to the hotel or consulate.
Some cell phones work in San Carlos. Some don't. I know Sprint does not. The calling cards available at the Mercado are usually the cheapest option for making calls back to the states. Everyone in San Carlos takes dollars. Almost everyone takes Credit Cards (VISA). Negotiating with vendors is expected. Don't buy with their opening price. Most everyone speaks English in San Carlos.
ATMs are available around town. They only dispense Peso's
Pack your suntan lotion, sunglasses, Imodium AD, whatever seasick protocols you need and lots of energy and patience. Holiday weekends are crowded. Leave early if you are leaving on Monday. The border will be hell! Better yet, leave on Tuesday!
End of May, you will probably need a 3MM and I would carry a vest and hood as a just in case. I don't get cold easy, so a 3MM is more than enough for me. By mid June most divers are in their bathing suit.
Lastly, as the water warms up; Jellyfish come out. If you are in full protection, you should be fine. But the "blue mals" have a nasty little sting to them. Avoid them when you can.
Have fun and a great time diving!!!!
jcf