San Francisco is quite walkable -- when I lived there, within a 5 block radius (roughly a 10 minute walk) I had 2 grocery stores, at least a half dozen corner markets, miscellaneous shops (dry cleaner, shoe repair, a cigar store, produce market, etc), numerous bars and restaurants.
The entire city is only 7 miles wide, so about half the city is within a 30 minute walking radius.
The entire city is only 7 miles wide, so about half the city is within a 30 minute walking radius.