You will regret buying a stick very quickly, and take this from someone who's lived in California for six years now. I don't know where you're planning on staying (North or South Cali), but I live in Southern California, and freeway traffic is a total nightmare.
It usually starts with a guy who was too busy watching the police officer on the side of the road cleaning up an accident to notice the traffic slowing down and rams into someone. When that happens, for the next hour, the freeway and anything behind it in that direction is stop, drive 5 MPH for about 10 feet, stop, rinse and repeat. And that's if the guy behind the idiot wasn't looking at the police officer too.
If he was... well... let's just say you'll be on the freeway for a few hours.
It's not always that bad, but I travel the 405 to the 5 North every day home from work, and right where the freeways merge there's a tunnel that's very prone to accidents either right before or right after it, and traffic EVERY night is a bitch.
I have a stick on my mustang, and it's my daily driver. KILLER on the leg. I would definitely recommend an automatic if you're gonna do some freeway driving out here. That's the thing about California... we use the freeways to get everywhere, so when the **** goes bad on the freeway, everyone gets ****ed.
BTW, if you are coming to So. Cal., let me know if you have any questions.