Land, breathe, explore.
Land at SFO around 3pm on Tue 18 Aug. Ease off the flight, then Golden Gate, Alcatraz, cable cars and the Mission. Collect the car only on the morning you head off — you loop back here to fly home on Sat 5 Sep.
Tip: Skip the car for these days — parking is dear and you won't need it.
Union Square / Nob Hill for central and walkable, or North Beach / Hayes Valley for more character.