I live in the East Bay about 20 miles from the City. This is a micro-climate area and it can be 70 degrees at my house and 55 in San Francisco. Its never really cold and we ride bikes on the road all year round. Its best to layer. In February it can be warm and sunny or cold and rainy. Its really just a gamble. You can go to Twin Peaks and see the city from a wonderful view, there is Union Square for shopping and eating, the Embarcadero area, Fisherman's Wharf, Chinatown. You can go to the Presidio and walk across the Golden Gate Bridge. Be sure to visit the Sports Basement in the Presidio. You can walk or drive down Lombard - the crooked street! Visit Ghiradelli Square, The San Francisco Zoo, the new California Academy of Science is a must - http://www.calacademy.org/ , lunch in Salsalito or Tiburon, Wine country - Napa Valley, Sonoma Valley, the spas in Calistoga, hike out to Pt. Reyes, or Muir Woods or Mt. Tamalpais. You can only do so much, so I would plan to rent a car or take tours. It all depends on what you want to do!