So as others have said, most dive operators on the West Bay/West End will take you out to the reef right off the west side of the island. Generally out to dive, back to the shop for your shore interval, and then back out for the next dive. West End Wall is a good site and will be close to where you are staying.
Some dives that you can do that are "different" (you can Google them for more details):
- the El Aguila wreck - This is neat. Probably not the best wreck you'll ever see but it's big and in about 100 feet.
- The Odyssey wreck - This one is further away so shops may not go to it often. I've been to the Aguila a bunch but the Odyssey only once and I wasn't feeling well so I can't really comment too much about it..
- Cayos Cochinos - this would be the "oh wow" place if you can get there. It's about 2 hours away? So you have to find a dive operator that is going and it will really depend on the weather since it's such a long trip. Basically you have a sea mount practically in the middle of nowhere that has a nice reef on it that is pretty healthy. If the dive operator includes it, there is a wall that's pretty good out there as well plus you can visit the Garifuna village. That trip will be around $200 though from Roatan. Oh, and this is where you might see a whale shark. I never have but this is where it could happen.
- There is a "shark dive" but I've never done it. I've heard good things but it sounds like it's run by this guy who's trained the sharks to visit and you just stand/sit on the sand and watch them.
- Night dive to see the String of Pearls. That will depend on how dark it is and possibly other conditions but if you do a night dive, ask if they will try it. That was super cool!
In general, sharks are very rare to see in Roatan. I think in the 10 years I've been going I've seen one nurse shark. Interestingly, when I go to Belize (which is not that far away), you see tons of nurse sharks and even reef sharks depending on where you go. But I think Rotan's reefs and fish close to the island are better than what you can see close to San Pedro (outside of the sharks). Lots of turtles, eagle and stingrays, morays, flounder, etc...
With regard to the bugs.... it really kind of depends. I tend to get bitten a lot but my wife not so much. If you are Infinity Bay you are probably okay because they sweep the sand in front of that resort every morning (and most resorts on West Bay beach do that). Some people say Skin So Soft works but I just use Off. Bring some itch relief lotion if you are worried? Maybe you will be fine? Maybe not?
Other things... we enjoyed eating at Celeste's which is behind the resorts. If Summer Dawn is singing at Grand Roatan, you can check her out at dinner one night. She's kind of a "one (wo)man band" and can be fun.
The reef in front of Grand Roatan is really close to shore so if you want to snorkel it's just up the beach from you. If you have a flashlight, you can even snorkel at night and maybe see an octopus (just don't get lost in the coral or you may have trouble finding your way back!).
Most places take US dollars but you should try to make sure they are new or newish and not really wrinkled or torn. You will get change back in both dollars and Lempiras.
A baleada is a Honduran staple so try one of those. It's basically a lazy burrito where they take a large tortilla, fill it with beans and cheese (and whatever else) and fold it over. In West Bay beach restaurants you will probably pay $5 to $10 dollars for one or two as part of a meal. In the West End you can find restaurants that will sell them for $1 (and an extra .50 if you add guac or chicken or whatever). They are a great light lunch between dives.
Finally, West Bay Beach (where Infinity Bay is) is gorgeous and if you like hanging out on a beach it will be awesome. But while you will have lots of dining options, most of them will be at the other resorts. This is not bad! It just is. Although Celeste's is a stand-alone restaurant. If you want to check out other bars/restaurants/shops, take a water taxi to the West End. It's the "other place" most tourists go when they go to Roatan (and where we go because we stay at a cheap place). The West End probably has better night life (but that will depend on the time of year). Try Sundowners if you go there.
One more thing! There are a couple of places/parks that let you hold sloths. We did that once and you just smile they are so cute.
