I live about 45 miles NW of the Chicago loop, I work about 25 miles NW of the loop. I used to live 25 miles due west of the loop. I've been pretty much all over the NW suburbs and I've never had any issues with my ATT Wireless when I am outside and above ground.
It does give me trouble in basements some of the time, but not as bad as my Ex (she has Verizon.)
That said, my grandparents live in the country in Door County, Wisconsin, and near their house, there is no signal until you get a bit closer to town....