If you already have a sat phone, take it along, but it's not worth buying or renting one. The down side of a sat phone is you can't call 911 in an emergency - the sat phone system doesn't know where in the world to route your call to. So to use one, you need to know specific phone numbers to call. And you can't call 800, 866, or 877 phone numbers with one. I do have a sat phone for snowmachining and hunting. See if you can get a non - 800 out of most airlines to make reservations on, or from Good Sam for road side assistance. We may have finally got one from them, but I'll have to double check that.
You'll have phone service when you get near a town. It's just about like the traveling we've been doing thru Arizona and Colorado. At least in Canada or Alaska if you break down, someone will stop to help you if you stand in the middle of the road and flag them down.
After we spent four weeks coming down from Alaska last year and not having cell service most of the way, I found it rather nice. Even after we got to where there was more consistent service, I'd go a week or so without ever missing it.
Bill
Nodwell RN110 out moose hunting. 4-53 Detroit, Clark 5 spd, 40" wide tracks, 10:00x20 tires, 16,000# capacity, 22,000# weight. You know the mud is getting deep when it's coming in the doors.