I don't live in SF now. I'd put an ad in craigslist to see if anyone close by will rent you a sliver of a garage. Or get a self storage place. I don't know if you've figured out the SF's bus system yet, but the Geary bus runs 24/7, and you usually don't have to wait more than 10 minutes for one, so (assuming you live close to Geary) you'd have fairly easy access to any storage place close to that line.