You are in luck. Bus travel in South America can be some of the most luxurious transport you have ever experienced. Most long-distance buses offer either semi or fully reclining seats. When I say fully reclining, that is to say they actually become beds.
I suggest the following itinerary:
Fly Buenos Aires to Iguassu Falls
Then follow this route I just suggested to another traveller a few days ago:
Bus to Asuncion, then another bus from Asuncion to Resistencia in Argentina, then over the bridge to Corrientes across the Paraguay River.
Then a long dusty bus ride across the Chaco to Salta. Daily at 18:00 x 12 to 13 hours. Semi-sleeper.
Now you take the Argentine bus to La Quiaca (Departing at: 5:30 - 10:30 - 15:30 - 22:00 hours), then cross the border on foot to Villazon and pick up a Bolivian bus to Potosi (daily x 12 hours) where you would change buses for La Paz.
If you really want a thrill, take the railway from Villazon to Uyuni and Oruro, Runs four times weekly on Sunday, Monday, Wednesday and Thursday (subject to change). Departs Villazon 3:30 pm. This is one of the few passenger railways left in South America.
http://www.boliviahostels.com/howtoget/tren.phpKeep in mind a lot of people like to stay in Uyuni to visit the salt flats.
Regular daily buses from Oruro to La Paz,
From La Paz, you can continue to Cuzco via Lake Titicaca. I suggest you stay at least one night at Copacabana and visit Isla del Sol. Puno in Peru is a miserable place, though a visit to the floating Uros Islands is interesting.
From Cuzco come back south to Arequipa (you might want to look into the Cuzco to Arequipa railway for the return trip to make a change). Stay a night or two there. You may want to take a side trip to spectacular Colca Canyon to see the condors.
Then a direct bus from Arequipa to Santiago. Not much to see on the way, just lots of desert.
Hope this helps, and keep in touch if you need more information
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