We did this only San Diego 13 years ago.
The best piece of advice for me was from a friend, there is a lot of really useful information in the front of the phone book :)
Also, expect that the language will be more different than you think and that people will expect you to not have any problems with it. One of my biggest issues was that I didn't know what brand names were good or what things were called. Frinstance, I didn't know what the DVLC was called here (DMV) and so it was hard to look up a phone number for it.
Expect it to be frustrating, stressful and bloody annoying (yet fun as well) for at least 6 months. Expect to still feel 'on holiday' (fantastic and somewhat surreal after a few months) or not really quite at home or fully settled for at least two years. Someone told me this before we went and I found it to be very true.
Expect it to be hard to have friends that you have no common history with and not to know anyone well enough to start with that you trust your kid with. That is hard and isolating. Finding a preschool was really important for me because of that.
Expect to want to pound your head into the nearest wall sometimes because some things are so inefficient and stupid compared to 'home' (but BTW it goes both ways)
Expect to have issues with the stupid medical system.
Expect that if you give California and its people and yourself a real chance to adapt that it could be the best experience ever, but expect it to be a while before you think that. Try not to hang around too much with ex-pats (makes it harder to assimilate), but if you can find one good one to be friendly with it will help with the frustration factor.
I'm the whole other end of the state, but if you have any specific questions you want help with feel free to PM me :)
If I had it all to do again I absolutely 100% would.