Phil,
Unfortunately the smaller local carriers are quite often the "problem". Especially when roaming in to a predominate carriers territory...draw your own conclusions on that! I suggest you go with a major carrier before your epic ride or you may hit all sorts of roaming issues when your local Colorado carrier doesn't have an reciprocal roaming, or billing, agreement with a local "Insert State Here" company...it often gets very ugly and expensive....
I currently carry a Motorola Droid Razr Maxx 4G, on the Verizon network, and it has been problem free. My wife has a Razr 3G which has also been problem free. Those are both recent upgrades, prior to them we both had a Droid X with no issues other than what I considered poor "stand by" battery time.