East Beach runs along the northern edge of Crissy Field in the Presidio. It is the only beach in San Francisco on the Bay shore, and since the restoration of the wetlands and sand dunes, it has become extremely popular with families and dog owners who share the space amicably.
Take the Muni #29 from the Presidio or the #30 to Broderick and Jefferson, then walk north to Marina Boulevard and continue to the Crissy Field parking area.