I rode the length of South America in 2005. I remember Bolivia most vividly. If I were to go back for a 2/3 week trip, that’s where I’d go because you get totally diverse terrain in a very compact area. If you can, riding across the Salar de Uyuni and camping on it, is absolutely fabulous. But so is the ride from Uyuni to San Pedro de Atacama.
Then again, if you’re travelling by yourself, I’d also suggest the Camino Austral in Chile. You have a variety of turquoise lakes, glaciers, temperate rainforest, snow capped mountains – all that! It’s also packed with cyclists so you’re not really alone much.
Peru is another story. I didn’t get on with it, but then I got robbed at gunpoint on my brief period on the Panamerica, which put a downer on things. It felt safe once I was off in the mountains.
Cheers,
Vik