Haight and Ashbury for a little amusement from the locals with their funny signs or go thrift shopping!
Philz Coffee somewhere in SF. Heard it's extremely good from friends and yelp.
Could go to Treasure Island at night and take a look at SF looking all pretty with its lights and such.
Mitchell's Ice Cream or Bi-Rite Creamery while checking out Dolores Park sounds good if the weather clears up a bit.
If time allows it, go on a mission to find all the hearts and take pictures with them in SF. Various maps can be found online. A few hearts can be found at AT&T Park, Union Square and other spots around the city.
Off the grid can be a good experience. It's a food truck gathering that happens in various places depending on the day and time. More info can be found on offthegridsf.com
Steer clear of the Tenderloin area at night if you value your life.
There's a bunch of other things I'd suggest, but I just can't remember them right now. Hope this helps!