Harbor Freight has absolute garbage.
I still shop there every once in a while and talk sh1t about myself while I'm there, but it's still fun to visit.
HF is good for cheap, use-once-at-home type of tools. For example, I have a few 1/4" die grinders. They are loud and not very powerful but, at $10, they are good for home use and disposable. The $80 portable band saw is surprisingly decent for home use as well.
There's one in Hayward and Newark across the bay.
Harbor Freight
39155 Cedar Blvd
Newark, CA 94560
True Value Hardware and ACE Hardware are small neighborhood hardware store chains that have a lot of stuff and they are all over the City.
You should also go to
http://www.grainger.com/Grainger Industrial Supply
750 Brannan St
San Francisco, CA 94103
Pick-N-Pull as suggested earlier is good. I would visit the one in Newark because the surrounding neigborhoods are not that sketch.
http://www.picknpull.com/locations.aspx?View=Detail&ID=47Pick-N-Pull
7400 Mowry Ave
Newark, CA 94560
It's an hour away, but you could go to Harbor Freight in Newark, CA then go to Pick-N-Pull down the street.
If you google maps these locations you'll see that it would be pretty simple.
Welcome to California,
Angelo