David Auletta wrote:
It's a personal recreation adventure! I don't think it will be safe or
easy but definitely fun. I'm not even sure exactly what I need yet,
I'm sure we'll find out at the borders. [snip]

If you are a US citizen then at least in Brazil you need a valid visa.
Europeans and Canadians generally have less problems. Unless you
are Portuguese and want to enter Paraguay 8-]
A visit to the embassy of the countries you like to travel is a good
idea, otherwise you will run into serious trouble. Many embassies have
web-sites with good info while the prisons are crude and unpleasant.
You will also need a carnet-de-passage for each vehicle.
As for digital modes: South America has fewer resources and so
repeaters of any kind are a lot scarcer than in North-America.
Here in Paraguay e.g. packet radio net is nonexistent.
APRS? About what are you dreaming at night?

Good luck and kind regards, Eike