There is a web site that will let people look for cell phone towers and antennas. And other types of towers and antennas too. http://antennasearch.com/
This site may be of some help in locating a place to go that is more EMF-friendly. You input an address and it produces a report. So you need to have a spot in mind before this will be helpful.
If anyone has found a "big picture" source of this kind of info, please let me know. I suspect, but do not know, that a map of the country's worst and best EMF areas does not exist. If one does exist, it must be a bugger trying to keep it up to date. But if someone finds something like this, it would be good to know.