You could consider parking at a BART station and riding in to SFO. Choose you station depending on where you want to go after returning. I often use the Millbrae station with the tall parking garage.

Parking would be free for the first two days since you leave on Friday night, $6.50/day thereafter. (Purchase your permit starting on Saturday.) Roundtrip fare to Millbrae is $8.50. Purchase your permit here:

https://www.select-a-spot.com/bart/

and print it out ahead of time, you can't purchase parking at the station.