Rent your gear from
Sport Chalet (several locations in the San Diego area; La Jolla-UTC shop is closest to La Jolla Shores/Cove). You may be able to get an entire weekend's rental for the price of one day. Call the store and verify this beforehand. I've had friends who have picked up rental gear on Friday evening and returned it on Sunday afternoon...and paid for one day. If you need to buy anything scuba-related, Sport Chalet has the best prices in the area. Customer service can be hit-or-miss, though. I've encountered very knowledgeable, helpful staff there...and some folks who really don't know what they're talking about. Bear in mind it's a chain of sporting goods stores.
With regard to exposure protection, you'll want at least a 7mm wetsuit, thick hood that you can tuck into the neck of the wetsuit, gloves, booties, and open-heeled fins. Many people like to layer a 3mm hooded vest underneath a 7mm. I prefer wearing my drysuit.
Join the
Divebums.com email list. A week or two before your trip, you could send out an email asking to tag along with experienced local divers. Include your training level, dive experience, and whether you have any experience at all diving in SoCal-like conditions (55°F-65°F water, 10-15 ft. vis, surf for shore diving, etc.). There's also a
Power Scuba Meetup.com group that is fairly active. If you want a formal DM-guided tour of La Jolla Shores or the Cove, I've heard that
Scuba Diver Girls are a good outfit.
Getting air fills at La Jolla Shores used to be straightforward, if not a little aggravating. OEX (about 2 blocks away from the Shores) used to be the place to go for fills. OEX closed its doors a few months ago, it now seems to be operating with more of an emphasis on kayak rentals halfway down the block, and some of the former OEX instructors have split off to do their own thing. I've heard that the instructors are providing air fills out of a convenience store next to OEX's previous location. I've been told that you have to call a number ahead of time to arrange for fills on an as-needed basis. Hopefully, the air fill situation will get straightened out as the summer approaches. Alternatively, you could drive to the La Jolla-UTC location of Sport Chalet in the Westfield Mall and get fills there.