I travel mostly by car, since I live in a suburban area with mediocre public transit and work in an even more suburban area with worse public transit, but when I go into San Francisco, Oakland, or Berkeley, I take BART (the train). You couldn't pay me enough to drive in SF. Every street is narrow and one-way in the wrong direction, and parking costs $25 if you're lucky. (Not to mention the $4 toll to get across the bridge.)
However, my car is a beat-up 20 year old Toyota, so I'm still going the cheap route.