I'd buy an unlocked/unbranded or unsubsidized ATT branded handset which does not force you to enter into another contract before knowing what service/reception you will be actually receiving. Since you will not be in a 3G service area, you could grab even a cheap gophone from Target or Wal mart to test out how ATT does in your neck of the woods. Verizon may be a good alternative so you at least wouldn't have to necessarily commit to ATT.
ATT does sell SIM only service, but in your case you will likely have to push hard for this since they want to lock you into some sort of contract.
There will be more info on how to do this over at howardforums.com. Some other folks who were in areas formerly service by Alltel (divested areas now w/ ATT) have commented on their specifics, AFAIK.
I live in ND and Alltel is merging with AT&T in Feb. I must pick out new phones to use on the AT&T network. I currently have a 2 year old Blackberry. My free choices are a Blackberry Curve, an HTC Avia or a Palm Pre (which I have eliminated). My primary needs include good picture taking, easy to read big screen, ease of use and email.
If I so choose, I may extend my contract by 2 years and choose between a Blackberry Torch for $100, or a Samsung Captivate for $200. My fear there is I could be stuck for 2 more years if I do one of those and I don't know what to expect from AT&T. My only other carrier choice here is Verizon, but I've been happy with Alltel for many years.
Does anyone have any suggestions for this dilemma? Thanks in advance.