Dude, asking if there are any freedivers in La Jolla is like asking if Belgians ever eat potatos.
La Jolla is OceanSwimmer's stomping grounds and the place has no shortage of spearos.
The cove itself is a decent dive site. Plenty of shallow snorkeling right off the beach. You can hit depths of about 60-70' within the preserve (an area where boats are excluded and where folks do a lot of ocean swimming etc.), and you could actually swim out to the canyon and set a world record in any discipline, if you are so inclined and are willing to brave the boat traffic. The caves are another cool area, as long as the cops aren't chasing someone through them (inside joke).
The Scripps pier is another famous dive site in the area.
Here's a site that has coordinates and detailed instructions for finding some interesting wrecks in the general area:
http://home.nethere.net/willisjs/wrecks.htm. Freediving to the Cabezon cruiser would be a pretty cool feat.
Here's another site w/ summaries of some of the more well-known shore dives in Southern California. Note that about half of the sites are near San Diego.
http://www.shorediving.com/Earth/USA_West/CalS/index.htm
Orange County has some nice sites (and nicer people) that are worth driving to visit, and you can drive up to Dana Point if you want to take a boat over to Catalina.
There are lots of boats that go to the Coronados and San Clemente Island too.
So, yeah, there's some freediving in La Jolla
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