If the OP is still about to go on their trip, a recommendation for a place to eat:
The Grubstake, which is a charming out-of-the way spot on Pine St., between Polk & Van Ness, in an old streetcar converted to a restaurant. One of the few places in SF that's open late at night (unlike NYC, they roll up the sidewalks there pretty early).
Although some caution here: I remember the place from the 2000's or so. It was founded and run at that time by a Portuguese family and actually had some Portuguese dishes. There were no problems that I remember.
However, they ran into trouble later on; they were in danger of being demolished to make way for one of those horrible piece-of-shit buildings they're so fond of putting up in the Bay Area these days. They somehow dodged that bullet, but the business has been taken over by new owners. And judging from the Yelp reviews, all is not well there; you have to pay in advance, for one thing.
Still in all, it's probably still a quite charming place, one of those few "only in San Francisco" places around. They're getting fewer and fewer as the city gets more gentrified, yuppified and overrun with snarky hipsters.
Few other places if you can manage to get there:
The St. Francis Fountain, on 24th St. just east of the Mission District:
Been there since the 1940s, and last I was there it looked like the decor hadn't changed since then.
American grill cuisine and yummy ice cream.
Pancho Villa, also on 24th but just west of Mission:
A great taqueria in the heart of The Mission (there are lots to choose from there but this one is particularly good).
They have the aguas frescas, like tamarindo and my favorite, sandia (watermelon), as well as great horchata (sweet rice drink).
And for a really out-of-the-way place:
The Tennessee Grill, on Taraval west of 19th Ave. in "the Avenues":
OK, this place will never win any awards for their cuisine, but it's one of my all-time favorite places to eat.
The food is not bad at all, just not anything that "foodies" would praise.
Simple stuff, like spaghetti and meatballs, meat loaf, burgers, fried chicken, etc.
All quite edible. And in an atmosphere that dates back to at least the 1950s.
You could take Muni to get there.
In fact, if you have any free time on your trip and want to explore the City and don't have a car, you could get a Muni pass that would get you on all the streetcars, the metro (subway) and buses, just not the cable cars.
Driving in San Francisco is a pain in the ass best avoided anyhow.
Or just pick a neighborhood and walk. (Maybe avoid the Tenderloin and Civic Center.)