Pier 39: we can do it. We saw the stores, ate seafood sandwiches, toured a WW2 submarine and an arcade museum. Ghiradelli Square and the Maritime museum, which wasn't worth it.
We went through a big park super fast.
There was a small Shakespeare garden as part of the larger park.
We walked around the Legion of Honor museum and lawn as well as the botanical gardens, visited Japantown, and generally drove all over the large, steep and crowded city of San Francisco.