I'm in NE Ohio, not San Francisco, but yes I've seen it and done it occasionally. Not full on fucking, but handjobs, hands down each other's pants; blowjobs... usually in a stall, or we go out to one of our vehicles in the parking lot. That was one of the benefits of me owning an SUV all these years, lol.
If you see more than one pair of feet under a bathroom stall, they're either hooking up and/or doing blow.
Depends on the bar your at, some will kick you out immediately for doing that out in the open in front of everyone.
I've also hooked up in the DJ booths, as well as the dressing rooms for the drag queens, when there were no queens performing that night. I knew the staff well at those places, and they were cool with me if I asked if we could use a room for a quickie.