Hi Myke!
San Diego is a great spot for us divers! If you are looking for more info on shore diving, the San Diego Council of divers will soon be starting it's annual
Rocks, Rips, Reefs series. These will give you a much better sense of some of the more popular local shore diving spots and how to go about it safely. Alternatively, there are
two volumes that go into a lot of great detail about the La Jolla Cove/Shores area, the first is widely available through the San Diego County library system (the second one not so much).
Power Scuba is a huge scuba group based here, and they frequently charter local dive boats at no-profit prices, so normally $30-$50 off public facing prices. They also host many shore dives and other events. They are currently doing a computer group buy (this one is entry and mid-tier models) so if you are interested that might be of use. They also host free
reef.org courses, which help you ID local plants/animals/invertebrates/ etc.
Our two big local charter companies are
Marissa and
Waterhorse . Local destinations are wreck alley, point loma kelp beds, and Los Coronados (you will need a valid US passport for this one).
If you are looking to dive on
Catalina Island's scuba park, there is a small rental outfit right at the park or if bring your own gear you can pay a porter a small fee and they will take it over for you. Scuba gear is permitted on the big Catalina ferry boats.
Most of the other big boats that do some of the other cool destinations in the local area leave out of San Pedro, Ventura, or Santa Barbara.
This thread was about the channel islands but these same boats will do some of the other cool spots.