Could I find my way around San Francisco without the use of my phone? To my surprise, it seemed that I could. What I did was this: I looked for real-world objects that I had noticed en route to the Marriott Courtyard earlier. For example, I saw a group of 10 or 15 bored Japanese teenagers hungrily smoking cigarettes in the entryway to a tiny cafe. I saw a health-food store with a weathered cowboy painted on the sign out front. The cowboy was supposed to look intimidating, like he was about to engage in a barroom brawl or a shoot-out. But he didn’t look intimidating…