My girlfriend and I are planning on taking a vacation in California at the end of the month. We're around for 2 weeks, and we're going to spend 3 or 4 days in San Francisco at the start of the holiday. And then probably another day in SF before we fly back at the end of the holiday.

So, two questions:

1. What do you recommend we do while we're in SF?
2. What highlights of Northern California should we make sure we see in the remaining 9 or so days of our vacation? We're thinking Yosemite or Lake Tahoe. Any other suggestions?