one of my friends got married at a private residence in the palisades and it was amazing, why not see if you can rent out a private house in malibu on the beach?
As far as the guests staying close by, I know that my friend who had her wedding there got a pretty good room block at some of the hotels in Santa Monica (we went to high school there) but when I went to the wedding I stayed in Culver City and it wasn't a big deal to get to the wedding.
As for San Diego, hmm La Jolla would probably be your best bet for something a little nicer, and why not get a nice hotel room block in hotel circle which is not that bad of a drive to La Jolla.
I will keep thinking about SD and LA for you, DreaW might be able to help you out more with OC