Start combing through OffStageJobs and Playbill jobs now. Look into internships, summer stock, anything that seems interesting. If you are able, go to SETC or the USITT convention-- SETC in particular has a job fair that you may find useful and I know friends who've had great experience networking and interviewing at both. Either way, your best bet is research research research. When I got out of school I was lucky to grab a temp job that was tangentially theatre-related, but did not get back into SMing until later in the year- this is almost entirely because I did not start sending in application soon enough (summer stock and long-term internships start posting ads Jan-March, generally). Because I live close to NYC and had some great connections, I landed on my feet. Speaking of that, don't feel shy about asking friends and mentors if they know of anything you should apply for/anyone you should talk to.
Because I went to college in Manhattan, a lot of SM friends have stayed there, but I also know a ton of people go where the work takes them when they first start out- a friend has been going from gig to gig throughout the country for about 2 years now. It just depends on what you think works for you.
And- speaking as someone who left school 2 years ago and is still with her parents- even if you move home, you won't necessarily lose momentum, especially in a city like San Fransisco where they have a fairly large arts community. It's just a matter of how hard you're working and how lucky you get, really.