Presidio Main Post picnic table area between the Presidio Visitor Center (210 Lincoln Blvd., cross street Anza Ave., facing the Main Parade Lawn) and the bathrooms next to Il Parco. (Map search: Presidio Visitor Center, Lincoln Boulevard, San Francisco)
There are parking kiosks all around the area to pay for Presidio parking, and free parking at Crissy Field East Beach for those who don’t mind a bit of extra walking.