Since you are in socal, you're in luck. There are usually plenty of organizations hosting fun safe events. Couple I know of:
http://www.gfos.net/serca/2005/bigwillow/reg.php
http://www.speedtrialusa.com/index1.html
If it's your first time out, I'd recommend the latter. The Streets is a slower course than big willow but still fun and technically challenging as it has several elevation changes, a blind chicane, and a banked increasing radius turn. Big willow is quite a bit faster but if you've not done this before, you should work up to it. Driving on a track is much different than driving on a street.
And do keep in mind, these are not actual races. You can stretch your legs quite a bit and let lose, but passing is limited. If you really want to get into real racing, you should start with a race car driving school to learn the proper techniques and work towards getting a racing license. I'd perhaps look towards getting a dedicated race car as well.
If you are talking about drag racing, California Speedway hosts street legal drags. You'll need to check their website for dates. You can also head up to palmdale to race on the Los Angeles County Raceway. Elevation is a bit high there but still a decent track. I'm not sure when they allow the racing, but I think it is more often that the California Dragway. Carlsbad may be an option as well, but I don't know much about it. Hopefully they've at least fixed the pit and return lanes as my friend said they were poorly paved. If you're okay with 1/8 mile racing, Irwindale has that as well...you'll have to check with them fot dates as well.