I'm sure it makes me sound like an old fart, but I'm with you 100% Russ. One of my most enjoyable memories of my time on the AT is cranking out a solid 20 mile day, cruising into a campsite or shelter in mid afternoon & apart from eating & getting water, having absolutely nothing to do but to sit around & talk BS with other hikers..........getting online & letting the outside world intrude on that would kind of spoil it for me........(old fart mode <off>).

But back to the OP's question..... Picking up a cheap pre-paid phone in the US is about as easy as it gets, drop in to Walmart, Best Buy or any other of the large stores and you can get something for well under $100 . Walmart actually have an entire category on their website for sub $100 phones with no contract