Hope you find someone to dive with.
In LaJolla you can either dive LaJolla Cove or LaJolla Shore.
LaJolla Cove offers some excellent diving with your choice of sand, rock reef, cave/cavern, kelp to dive, all in one spot. Nomally lots of life as this is a preserve and some excellent diving. If you enter at the stairs and proceed on a heading of 30 degrees toward the bouy, then dive down at the kelp just short of the bouy about 50 yards, and continue on your course of 30 degrees, you should, if you are luckly, come upon a grooming station for Giant Black Sea Bass. I saw a dozen there one day, along with some blue sharks on the way in. Currently they are reporting lots of soup fin sharks in the area which are a treat to see as well. Tnis is one of my favorite sites.
(The below is both my own observations and from reading A Diver's Guide to Southern California's Best Beach Dives by Dale & Kim Sheckler, a must read for diving Southern California)
LaJolla Shores, (easiset access is Kellog Park) used by a lot of dive classes, is a sand bottom and there is, in my oponion not much to see here, unless you go into the canyon, except maybe at night when stuff comes up out of the canyon. The canyon, wich is about 100 to 150 yards off shore dropps off very steeply, some even refer to vertical walls of 20 to 30 feet which stair step down into the deep. There are two main branches of the canyon. The Northern branch, called Scripps Canyon is reported to have spetacular vertical walls and you can get to over 700 feet here just one mile from shore. But the canyon is a long swim out. The Southern branch is the Lajolla canyon. You can get to 700 feet here too if you want (well above the recreational limits). Just 100 to 150 yards off shore you go from a bottom of 45 feet to 200 feet in the space of 100 yards.
The life is in the canyons if you are at the Shores.
There is lots of good beach diving in San Diego in additon to the two sites above. Good luck and have fun.