The fairly new De Young Museum is one of the great museums in Golden Gate Park. They have a nice outdoors sculpture museum and then displays inside. The last year we were there was a special exhibit of Chihuly glass work, which we've seen in several different venues (Kew Gardens, Chicago Botanical Gardens, etc) and always enjoy. Another year there was an exhibit of wonderful quilts made by a group of descendants of slaves. EAch year there is something different and something worth seeing.
There is also a terrific tower attached to the museum with outstanding views of the city and the park.
From journal Two Weeks in San Francisco