This that you WANT to not miss while you're here:
1. THE Porchetta sandwich from Roli Roti on Thursday and Saturday at the Ferry Building at noon. Only on those days at lunch, farmers market is a great way to spend some time walking around. A bit pricey, but well worth your experience. Do come early. Long line. Long. Oh, and if you want some of the better rotisserie chicken, then the same place (but you don't have to stand in line, just go up to the counter).
2. While you're there, schedule a trip for Alcatraz. This week is suppose to have nice weather, so schedule for it after your pork sandwich in the afternoon. By then the fog would have burned off and you'll have a GREAT view of the bay, the bridges and the city. You'll need to book your Alcatraz trip in advance.
3. Up the street a bit is SFMOMA, right now they have a few note worthy exhibits, one of which is the Picasso, Matisse and the Parisian Avant Garde if art is your thing.
4. If you want Chinese food, take a trip down Irving or Clement. But, I'd recommend two places. One is Hong Kong lounge on Geary, the other is R&G Lounge. They're both excellent and Hong Kong Lounge is a bit grittier, so if you're staying around downtown, go to R&G Lounge. Do treat yourself to the Peking duck there, it's the BEST I've had, and believe me when I say it's possible some of the best Peking duck in the world. I can say that with authority. Order the whole duck. The black lychee Martini at the bar is great.
5. You can walk around China Town afterwards, then straight to Union Square. Make a detour to the Marriot hotel. Take the elevator to the rooftop bar, have a drink or five there and enjoy the view. If you see any Singapore Airline or Malaysian flight attendants there, say hi for me.
6. Fort Point at the base of GG bridge. Picture ops. You may be able to see some surfers out there at the right time. Spend some times driving through the Presidio. It has some amazing and breathtaking views.
7. Japanese tea garden in the GG park.
8. Cliff House - have some clam chowder
9. Walk to the Park Chalet - a few more drinks.
10. Take the bus to the SF Zoo, you'll like it.
11. Say hi to SSSnail.
12. There are probably TONS more things to do, but I don't remember all of it. Whatever you do, don't go to the Mission, or Hunters Point, Bays view, or cross the bridge to Oakland.
13. As much as I hate it, but I think you should rent one of those three wheels driving guided tour. It's something I'll do one of these days, and I think it takes you to all the usual places.