I have heard that there is a fabric district in San Francisco. You should call their board of tourism, or your hotel concierge for directions and maybe a list of local quilt shops. I don't think there are many right in SF. Maybe you can amuse yourself at Pier 39 and Ghiradelli's Chocolate Factory?
There are several in the Sunnyvale, San Jose and Monterey area, but that is a few hours drive. I'm sure you can find a lot of quilt shops if you do an internet search for the Bay Area.
If you want to have fun on one of your other 6 days together, go in to Palo Alto and eat at the Creamery. There are lots of cute shops right there also. I love the kitchen shop, but can't remember the name.
San Francisco is a "strange" place, so I wouldn't wander too far alone for any kind of shopping!