We are Canadians currently in Arizona. For phone we use Tracfone. Can add time whenever needed. Tracfone can call anywhere in North america including to cell phones which some pay as you go plans don't.
For data we are using StraightTalk which is also pay as you go. It is a subsidiary of Tracfone. Data costs $40 fr 4 Gb which is good for 60 days. You can add more data at any time. The data does not carry over the way the phone minutes do with the Tracfone.
Both systems use Verison towers. We have had very good coverage in our wanderings. Right now I'm using the hotspot in Organ Pipe National Monument in Arizona by the Mexican border.