First thing to note, of course, is that sharks are wild animals and can bite whenever, even if that's a relatively rare occurence. Lots of great diving off La Jolla, including the Marine Room, which is a shore dive where there's a good chance you'll spot leopard sharks during summer. Check out http://www.sandiegodiving.com/diveSites/items/9.html for more info. Naturally, I'm assuming you're certified; if not, sign on with a local outfitter like OEX (http://www.oeexpress.com/La-Jolla-Store.html).