Conversely, I spent two weeks driving an RV from Chicago to Burning Man (where I had coverage on the playa), and then back to Chicago through Yellowstone. Yes, I had a roaming data cap, but it was higher than yours since I'm on the unlimited $50 voice/text/data plan (I believe I get 100MB/month of roaming data).
I can't really complain when my wife was sending MMS pics back home of Burning Man from inside our RV. That's coverage.