I've been to San Francisco several times, and roamed a lot of places, and I have to say I'm disappointed, since I've never seen a guy in a speedo on the street. I DID see skimpy dressed guys, inside the fetish shops. Not on the street. If you went during one of the festivals, yeah, you would see lots. Maybe you're hitting the wrong time of year?
And if you(the op I thinksaid it) are not comfortable around gay people, you might not want to go to San Francisco. I'm not saying all of them are gay, but there is a LOT of gay people there. Especially in bars. Especially in GOOD bars. And the guys are OH so nice to look at... maybe next trip they will wear their speedos.