Depends what part of the bay area you're in. If you're on the Peninsula, one of my favorite routes is 92 East towards Half Moon Bay, turn left on HWY 35 (Skyline) which follows the hills south. Stop at Alice's (intersection of 35 and 84) for a break. Head right on 84 out to the coast.
There are a lot of other little side roads along there too that are fun. So depends on how much time you have as well.