If you like museums, I'll be happy to gift you a ticket to the De Young to see the David Hockney Exhibition on Saturday or Sunday. PM me if interested.
The Alcatraz evening tour is worth it.
Hanging out getting sun in Dolores Park during the day is fun and social. Be careful of buying brownies (unless it's from "The Truffle Guy") unless you want to get really, really stoned.
Bicycle over the Golden Gate Bridge.
Check out the food stores at The San Francisco Ferry Building.
Polk Street at night. Try "Upcider" bar. Not gay, but good.
If you like funky jazz, Fillmore Street at night. But, be careful.
Be careful of the Mission district and the Tenderloin district at night.
Chestnut Street in the Marina and then checking out Ghirardelli Square at Fort Mason are great on a clear day.
The Wharf is completely tourist. Union Square is completely tourist.
If you like it rough, some of the gay bars in SoMa are the place to hang at night. Take a cab. Don't bus or walk it.