A friend just emailed some suggestions what to do while stuck in SF:

20+ campfires on Ocean Beach

A fun thing to do any Friday or Saturday night after about 8pm until
after midnight is go to Ocean Beach where hundreds of people make 20+
campfires (folks are friendly -- just walk up and introduce yourself
and join some group's campfire or walk between many -- bring some beer
or snacks to share if you want to).  This beach is at the intersection
of Great Highway and Fulton street, San Francisco

https://maps.yahoo.com...

Apparently, SF is more European than US on average, since you also have:

San Fran nude beach

If nude beaches are your thing, the weather looks nice and warm this
weekend, so try Baker Beach in San Fran  (don't go if you are
homophobic).

near the intersection of Kobbe Ave. and Lincoln Blvd., San Francisco:

https://maps.yahoo.com/#mvt=m&lat=37.79878...

I appreciate, and will consider the suggestions! (There was also a bunch of restaurants, museums...)