You have come to the right place for a dive vacation, but only one day? Ok Boat diving is a great way to do it. 3 tank dive will run you between $80-$120 depending on boat. The great Escape is an excellent choice for about $100 and both air and food are included in the price. You can board the night before and sleep on the boat. But most Long Beach and Los Angeles area boats only operate on the weekend. In Ventura for $75.00 you can take a trip on Wednesday or Thursday. San Diego offers dives most days of the week on smaller boats.
For beach diving, well we have some excellent beach dives here. Laguna Beach offers some very good diving with stairs down to the beach. Palos Verde is great diving, but most sites are, well, sort of trails. Malibu offers improved trails to most of the dive sites.
Word of caution, don't know your beach diving experience, but it is more physically demanding than boat diving. First there is the hike to the water in full gear. Our topography is such that most of the diving beaches lay at the bottom of cliffs of 50-160 feet. Thes meand there is normally a bit of a walk associated with beach diving here. This can just be a walk down 50 to 150 stairs (and back up again after the dive) and then the swim out from shore of 100-400 yards. It can also be a hike down a goat trail or worse, it all depends on the location. If you cannot comfortably climb 4 flights of stairs at a good clip (beat the elevator or close to it) then you might want to work on that.
Tank, wetsuit (7mm suggested) with hood, weights, computer, compass, BC, and regulator can be rented for about $45-$60 depending on where you go. Sports Chalet offers tank, wetsuit, computer, compass, BC and weights for $45.00 for a day (defined as pick up one, day, dive the next day, and return it the third day before closing). You will need to bring your mask, gloves, boots, snorkel (required in Laguna Beach) and fins. There are two places that will rent everything (mask, fins, snorkel, boots, gloves, wetsuit, regulator, tank, weights, BC and compass) for $100.00 per day.
Don't forget to allow 24 or more hours after your diving before flying.
May 1st is a Sunday and May 4th is a Wednesday. Don't know where you will be staying or what day you want to go diving on. Sunday the Sandeaters will be diving someplace. Their schedule for May is not yet out.
http://www.sandeaters.org will give you a description of many of the local dive sites including photos from off shore back to the beach.
Where to go is up to you. Check the sandeaters site for description. But here is my recomendation:
Laguna Beach: Crescent Cove, Shaws Cove, Heisler Park (divers and fishermans cove) due to easy access by way of stairs.
Malibu: Leo Carrillo (park at the sand), Malibu Road, Corral Canyon, Escondido Creek, Nicholas Canyon, El Matador, Sequit Point. Improved trails and/or stairs.
Palos Verde: Malaga Cove and Haggerties (with entry at Malaga Cove and swimming over) as it has a paved road you can walk down (long and steep), or old Marineland with its dirt road down (walk again, no cars allowed).
Redondo Beach: Vets Park (stairs, but not many) and Topaz Jetty (stairs, a bunch).
Anaheim is closer to Laguna Beach so that may be the way you want to go.
I am available to dive on just about any day of the week at Malibu, Redondo Beach, Palos Verde or Laguna Beach dive sites.
177 dives todate, all but 18 or so off the beach (hey, its cheap), but only 79 of those were this year. Plan on getting 4-10 more dives this year, weather, and wife permitting.