adding to @mom2and 's post, the Presidio, Lands End, Marin Headlands, etc. are all part of the Golden Gate National Recreation Area. 140 miles of hiking https://www.nps.gov/goga/planyourvisit/hiking.htm
Just opened in SF: https://sfist.com/2019/06/03/new-17-mile-san-francisco-crosstown-trail-connects-citys-parks-hiking-trails-and-little-known-outdoor-gems/
Also…they could take ferry to Angel Island https://angelisland.com/top-3-hikes-on-angel-island/
All of the above accessible by public transit. Yes, it could be rainy in November…but guessing if they are hikers, they will be equipped. My one suggestion if they do it is to make sure maps are downloaded…connectivity is not always guaranteed in these areas! Enjoy!