If you are right downtown, a rental car will be expensive to garage and tricky to get around in. It's not like New York City, or even Boston, but San Francisco is the most East Coast city on the West Coast with narrow streets and a jumbled street grid at times. Perhaps in this age of nav systems it's not as bad, but I remember driving around San Francisco in the 20th century and it could be daunting. There's also the added cost of garaging the car overnight at your hotel; that won't be cheap.
Do you Uber? That can be great. Otherwise, taxicabs and a streetcar or cable car or two and a good pair of walking shoes.
What about museums? San Francisco has several of the nation's best art museums, several near the Disney Family Museum.
The De Young museum in Golden Gate Park is wonderful and comprehensive, and one of two main museums focusing on Fine Arts. The Legion of Honor is the other fine arts museum, but the De Young has a great observation deck that looks out on Golden Gate Park and the California Academy of Sciences across the green, and beyond to the Pacific Ocean.
http://deyoung.famsf.org/
California Academy of Sciences is your typical big city science museum, but is thankfully aimed at adults instead of "wacky" exhibits just for kids. Excellent planetarium shows, biodome exhibits with fish and fowl and animals, rotating exhibits, and a fascinating living roof to wander on.
http://www.calacademy.org/
The Palace of the Legion of Honor is the other major fine arts museum in town, not far from the Disney Family Museum, and with stunning Golden Gate views. You'll find collections mostly dedicated to American and European artists here, in mediums ranging from paintings to dresses and gowns to silverware and china. One of the country's finest collections in a grand facility.
https://legionofhonor.famsf.org/
What about getting dressed up for cocktails, or a snack, at the Top of the Mark? You can't get more San Francisco than that!
http://www.intercontinentalmarkhopkins.com/top-of-the-mark.aspx
