I spent a decent amount of time in SF, It is an amazing city, walkable everywhere, but obviously stay alert and get ready for some serious hills.
Alcatraz still remains to this day the best day out ever..!
bike the bridge to Sausalito is cool, when you get there get the ferry back, it’s part of the deal, but watch out if you leave it too late in the afternoon as the ferries get chock full of people and you could end up waiting a couple of hours.
Along the embarcadero is an experience, go to fisherman’s wharf with the rest of the tourists for a look at the sea life.
If you have access to a car then go north and get out of town to Muir Woods and see the giant trees, they are mind blowing.!