Saturday morning is Farmers Market at the Ferry Building – but really every sunny morning is glorious there. The fog lifts first in this area of San Francisco.
For lunch you have two options – go to hipster central the 'Mission' or take on the Golden Gate bridge.
The Golden Gate bridge is an awesome sight – and the fog just adds to the experience in my opinion. If you have a car/bike it's worth going up the hill immediately on the left (Conzelman Rd) for some seriously spectacular views. Then head for Sausalito and stop by Bar Bocce or Sushi Ran for lunch.
Go back to San Francisco by ferry for more scenic views.
At night head out to one of these culinary (but affordable) temples: