My husband is from SoCal and he loves Seattle. If you dont mind rain, its close enough for cheap flights and I hear it is amazing and the people are cool. Same could be said for Portland, which is a bit closer. Both these places are beautiful. Some people find rain depressing, so if you are one of those you might reconsider. Another close choice would be Phoenix. Now, I know lots of people that love it and it is within driving distance so you can come home as much as you like. You just have to ask yourself if hot weather and the desert are cool with you. The desert and heat can be awesome, and I like them. The people are great there too. Its a little smaller so it might not be as scary. Your other choices are not really logically close enough to go home very often without spending lots of cash. Although if you wanted a real adventure far away...Toronto is an awesome city. It is very clean beautiful and friendly.
Dont leave california. california has alot of good medical schools including the long list of UC. If you were to leave i would say oregon. The trees and scenery are the most beautiful things i have ever seen. Arizona isnt very user friendly in the summer, and i havent met very nice people there...
My vote is absolutely on Portland, OR... because of how close it is to California and it is sooo beautiful there and has a strong art culture as well... my second choice would be Seattle if you don t mind rain... but those fit what you are looking for in culture and in distance convenience...