I've only explored San Francisco to great extent, living there for a few months, and I lived in L.A. for two years, so I'm not too familiar with the rest that California has to offer.
Ninth, I don't exactly know what your interests are so my ideas are from the hip. For when you are in S.F., take the requisite stroll up Powell Street downtown. Start at bottom of the hill, at Union Square, and go north on Powell (forget the cable cars - too expensive now and the queues are insultingly long, unless you want to be elbowed by bustling Chinese locals who will all get off in Chinatown to do their shopping). Going up on Powell, it's mostly tourist trap souvenir shops at first, then it becomes hotels, cafes, and bars.
When you reach the Sir Francis Drake Hotel go a few doors up and on the corner of Sutter St. should be a nice cafe to sit and have breakfasts of croissants, fruit, and coffee, and people watch (forgot the name). Many 'Woody Allen types' go there (they work nearby or live in affluent Nob Hill). Continue up the hill and you'll find yourself in Chinatown, a gorgeously busy area. I'm not usually the outgoing type but I just LOVE being amongst the locals rushing around shopping. Hidden somewhere in Chinatown is an awesome old store that sells musical instruments from around the world (like Tibet, Africa, South America). If you find it please grab a business card and let me know where it is. I've been there twice but keep forgetting exactly where it is.
Walk further up on Powell and you'll leave Chinatown and enter the Italian flavoured North Beach, the only neighbourhood in S.F. I seriously want to live in. It has a shitload of wonderful cafes, idiosyncratic Italian eateries, and sweet little park, Washington Square, with its own church.
Let me know if you want more suggestions.
