Welcome to my neck of the woods!
In SF, you should visit TAD Gear and the Spy Store. -But you may have access to cooler stuff than what's for sale.
If you're here with someone special, you should visit Napa or Sonoma and do some wine tasting. They are about 2 hours north of San Francisco.
If you can, visit Big Basin Redwoods State Park south of SF and halfway to Silicon Valley. They have trail loops which can take 1 hour, 1/2 day. If you like looking at big trees, the Father of The Forest is over 2000 years old and stands around 329 ft tall.
If you have a day to spend, visit Silicon Valley which is 1 -1.5 hours south of SF, and see where a good part of the world's technology originates from. Drive south on HWy101 0r FWY280 to San Mateo where Facebook is, then you can take a whirl around Stanford University and shop at the Stanford Shopping Mall down the road. Hewlett-Packard HQ is also located nearby.
Then head south to visit Apple Inc. HQ in Cupertino, they have an Apple store which sells more Apple gear than technology (just look for the tourists having their pictures taken in front of the signs). Next would be Mountain View with Google HQ and YouTube. Then head to San Jose where Intel HQ is and has a museum, there's also the Tech Museum in San Jose, as well as the Rosicrucian Museum, which has the largest private collection of mummies in the world. You can also visit the Winchester Mystery House for the tour (it's OK), but the see the gun museum which is spectacular. Finish your San Jose visit by crossing the street to Santana Row, which is the hang-out place in Silicon Valley. -maybe place an order for a Tesla motor car while you're there.
My office is within walking distance to Santana Row, PM me if you want to meet for some drinks if you visit.
As a Bay Area/Silicon Valley native, PM me if you have any questions or special interests you'd like to see.