In NYC (urban areas in general) there is a ridiculous amount of Ingress content. You'll meet a ton of players and level up very quickly. Even on foot. I live out on Long Island (east end, in the sticks) and Ingress content is few and far between. Not feasible without a vehicle. I imagine it will be similar with Pokemon Go: rich content in high-population-density areas, and not so much elsewhere.
Similar in concept only. With the popularity of Pokemon I think you'll have to search far and wide NOT to find other players.