We stumbled on Crissy Field Beach having no previous idea it's a legally off-leash dog beach! Yes, you need to pick up after the pooch, of course. This meant a delay in reaching the bridge, naturally.
All in all, we walked 9.5 miles (not counting major romping time at the beach). You could make it much shorter by leaving out walking the other way to Ghirardelli Square, or by parking nearby the beach - where I actually saw parking.
Limited food access on a Sunday. We stopped off mid afternoon at the Marina Safeway, which was a few blocks from where we parked on Bay.