I have TMobile, as well. The only place I've ever had a problem was in some areas of Fort Wilderness. I had no signal in the lobby building, but a couple of bars on its porch; no signal in the RV, but a couple of bars at the end of the pad. But I've used the same phone (a Nokia) in all four parks, Downtown Disney, and at the Grand Floridian, the Animal Kingdom Lodge and the All-Star Music with no problem at all.