I've been to Argentina 12-15 times, but always business and never more than 90 miles from Buenos Aires. Same for Brazil, but almost always Rio or Sao Paolo. Took my wife and three kids to BA and Rio for two weeks in 2001. Had a seriously awesome time.
A few of my best friends in the world (literally) are from those places. Even though they often shake their heads at how various U.S. administrations have treated them over the years, they have great respect for America and Americans and I was always graciously welcomed by everyone I met.
For scenery, I think you're barking up the right tree to go to southern Argentina. I was told, however, that turistas outnumber natives at all the resorts and ski locations down there. True anywhere I guess. I always wanted to go north out of BA to the Brazilian border to see Iguazu Falls.
Peru is pretty ass-backward. It's charming and quaint but can be scary because the third-world quality of the place is overpowering. Some 70 percent of the homes in Lima, the capital, don't have running water. That's a "city" of more than 8 million. Something like 15% of people in Lima have a phone. I usually felt safe, but looking back, I was probably stupid. I wanted to go to Machu Pichu since I was in high school sophomore Spanish in the 60's but never had time to go.
Chile and Uruguay are good visits. Paraguay has always had a bad reputation and I never went. Venezuela and Colombia are OK, but I was always with locals I knew through business and never felt unwelcome. Panama is fine. Costa Rica is where we should all retire. Guatemala can be spooky but even the Guatemalans don't want to go to El Salvador or Nicaragua.[/QUOTE
Nicaragua is poor, but safe. Beautiful with much to do and see. It used to be resort free, but this (unfortunately) is no longer the case.