For all leads/contacts who have registered we do track their IP address and get a location based upon that IP Address.
The IP address that we get and create the map from, is based on the IP address of the hub of the ISP (Internet Service Provider). We pin-point the location of the network hub, not the actualy physical location of the person. So what this means is that there is a very good chance that the people from the same area/neighbourhood will have roughly the same location.
You should be using the map/location for the City, as the City is typically pin-pointed with a 99% accuracy. But that's not possible for deeper level i.e. neighbourhood.