Lead is only banned for hunting. You can target shoot with it. Lord this thread has a lot of FUD in this thread by people who "visited" or "lived here for a year".
Join Cal Guns. Don't stress. San Diego has the best weather on the planet, fantastic restaurants, some really great museums (the Air and Space is fantastic as is the USS Midway), a cool downtown area, an amazing baseball stadium (albeit with a [bleep] team), and has some nice rural areas inland. There are plenty of places to shoot as California has way more gun owners then Maine, Montana, Colorado, etc. probably combined LOL. Some ranges are membership only, but most are not in my experience. If you are into IPDA or IPSC there are some world class clubs and ranges for those games.
That said. There are some good ranges but the ones I know of are up north east of LA. I like Angeles personally. I think it goes out to 600 or 800 yards with steel targets. Has a great shotgun range and is typically populated with pretty normal shooters. It will be a 2-3 hour drive from SD depending on when you go so make it an all day event.
Traffic will suck, big time any time of day, and it's expensive to live here. Enjoy it since you don't have a choice!
