Further to Flying Lawyer's post, I did some flying from Gillespie last year. I didn't fly there pre 9/11 so I can't compare but I experienced most of his recommendations when I was there:
Coronado/Bay: There is a VFR corridor over Lindberg Field (the international airport at San Diego) between 3300' and 4700' with no ATC permission necessary. If North Island Naval Air Station are feeling friendly they will let you fly along the coast just off Coronado but they'll probably ask you to remain below 500' (shame...). Then you can ask Lindberg if you can continue up the coast at the same height which they usually agree to. Just watch out for the banner tow aircraft advertising on Mission beach. You can then fly along the coast all the way up past La Jolla and up to Del Mar. As Flying Lawyer says, La Jolla is also worth going to by road.
Catalina is definitely worth a visit but the approach is quite sporting. Santa Barbara is also a good day out if you fancy going a bit further afield.
You can still fly over LAX via a VFR corridor (not sure about the route). I landed there a few times IFR - which was epic! LAX is the only place I had to pay a landing fee ($25).
Gillespie and Montgomery are both very friendly although Montgomery can get extremely busy (more so than Gillespie).
Have fun!
Samson.