If you’ve got a car, good company, and some time to kill, camping in the Bay Area is just a stone’s throw away. Saturday night campsites are generally booked months in advance. Weeknights? You’ll have a better chance.
I was stuck in the Bay Area one Saturday for a Chainsmokers concert. A quick browse on recreation.gov showed a Friday night Glen Camp site at Point Reyes National Seashore. I whipped out my credit card with lightning speeds, and within seconds, a campsite nestled in the woods was mine.