Mark Twain once said he never suffered a colder winter than August in San Francisco. Take warm clothing and prepare for fog. Santa Cruz has one of the few remaining boardwalks on the west coast. The boards have been replaced by cement, but the tacky atmosphere persists. Eat lunch or dinner at Riva Fish House on the pier and watch the gulls, pelicans and surfers.
Some wineries charge only a few dollars for a wine-tasting session.
Yosemite Valley National Park is a rock climbers paradise, and generally overcrowded. But vey beautiful. Go if you have time and love the mountains. Or visit the Lake Tahoe area. Both are about a four hour drive from Stanford.