It is a great way to see the city. The best way is to get a 48 hour tour; then the first day ride the entire tour and decide where you want to get off. Then the second day hop on and off at the stops you like. If you get an early start, you can do it the same day, but I have been 3 times and I would advise the 48 hr tour. If you can read maps, the subway is much less, because you can get an all day pass for $7 per person and go everywhere MUCH faster.