I'm not from socal, but I have spent a little time down there. My summers are spent at prime varmint country in Bridgeport CA in the eastern sierras right at the NV border. I shoot a ton of ground squirrels, and I'll bet you could probably in the foothills in socal. Here's what you need to get hooked:
1) .22 rifle. A scope is nice, but because of the ups and downs where I shoot varmints, I do a lot of standing shots with max range of 75 yards. Anything longer I bust out the .223. My CZ452 has excellent adjustable sights, so I do not use a scope, besides it's great practice.
2) Binoculars, even if you do have a scope.
3) LOTS of ammo.
4) But most importantly; a place to shoot! Most ranchers have no problem letting you take out varmints on their ranch. Problem in socal is finding an area where there are no obstacles, but I'm sure you are resourceful enough. If you can't find anything in socal, try the central valley, I know of a few guys that shoot there all the time in the winter.
If you want to maybe find somebody in your area that shoots varmints and could get you started with #4, I suggest talking to the good folks over at varminthunters.com -->main board.
Cheers!
Blair