Get a Kawasaki KLR; most of the roads are dirt.
If you're hitting Brasil, go to the Foz Do Iguacu
It's amazing. You can walk across the bridge in town to the ftz in Paraguay and shop also.
And don't miss the churrascorias; there's one on the outskirts of Brasilia that's amazing.
Go to Curtiba and then to the old city on the coast there. The ride down the hill is scary (cobblestones) but worth it.
Hope you speak Spanish and Portuguese...