Since the cities are in North America, NAD 83 would suffice as would WGS84 if you don't want to do a datum transform. Since you are working at a city scale, the difference will not be relevant. And there is a good chance that the whole city falls within one utm zone. Just match your city to its location on a utm map. If they don't fall in the same utm zone, and you want to map them together, the US, often uses an Albers projections in that case.
