I made a road trip from California to Vermont and back this June. I started off using Simple Mobile which operates on the T-Mobile network because it has the best connectivity at my home. Heading Northeast from San Diego through Utah and Western Colorado I had decent service through Denver. I lost service East of Denver and did not regain it again until half way through Kansas. Coverage between Kansas and Vermont was generally satisfactory except in some extremely rural areas. On my return trip I was a bit concerned about weather conditions and decided that I wanted better data coverage. I bought a prepaid Straight Talk sim kit at a Walmart in Ohio and switched over. The sim kit has sims for connectivity on the T-Mobile and AT&T GSM networks as well as provisions for connecting on the Verizon and Sprint CDMA networks. I selected the AT&T sim and I had pretty good coverage through Michigan, Wisconsin, Minnesota and North Dakota as long as I was on a major highway. Coverage in Montana was a bit spotty because we were headed to Glacier National Park near the Canadian border. I had good coverage all the way down the West coast. The cost is reasonable at $45 for 30 days unlimited talk, text and 5 GB of 4G LTE data and unlimited 2G data after the 5 GB is used up.