Where you can buy a house really depends on a lot of things - first and foremost, what are your needs and what are your goals?
Do you have a special location in mind and want to narrow it down? Where do you work, do you have to worry about the commute? What are your speciality? If your job does not work out, will you need to find another one in the same field? How many jobs are there for that field and where? Do you have kids who go to schools and need to be in good school district? Do you like outdoors or the convenient of the city? Do you like to go hiking, surfing or do you want to be close and enjoy the city culture? Do you have to be close to public transportation?
Do you like it to be sunny, warm, windy or calm?
Of course, we can not overlook the finance issue. Have you talked to the mortgage broker and find out what is your comfort zone when you look for house? That will also help you narrow down where you should and can look.
San Francisco Bay has such a variety of areas for you and so much to offer. So my suggestion is for you to find a reputable realtor who will be help you from getting financing to narrow down to the specific area, to finding the right house for you, to finally close escrow.