The first thing I would do is buy a 3-day MUNI pass for you and your friend. Driving is OK but parking is impossible in SF. The F Market line (a collection of neat old trolley cars) will run very close to your hotel and will take you to Fisherman's Wharf in one direction and to the Castro in the other direction for the, er, evening activities.

I can't even begin to suggest any restaurants because there are so many good ones in SF. Check www.zagat.com and www.sfgate.com for recent restaurant reviews.

Napa is my favorite day trip from SF. I would rent a car for the day only (that parking thing!). Another half-day excursion is to take the ferry to Sausalito.

If this is your first time there, your problem is going to be deciding on what _not_ to do. Have fun.