General aviation flying in South America is generally a great experience. Beautiful scenery, friendly people, less traffic than in the US or Europe. Service at most of the larger airports is great. Most larger airports have good weather service. Keep in mind there's always possibility of convective weather around the equator.
Having said that, there is a fair amount of bureaucracy. I recommend using a handling agent to take care of landing permits, overflight permits, etc. You can do all that yourself, but in my opinion not worth the time and hassle.
If you want to take the really scenic route you could fly down via the Caribbean and Brazil, and return via the West side of S. America. In a C182 you can comfortably go Miami - Montego Bay - Cartagena - Cali - Guayaquil - Trujillo - Lima. All those places have avgas.
Lima to Miami by Cessna 182 « Contract pilot tales
I remember Trinidad having avgas many moons ago, best check but I think it still has it. I believe Manaus as well as some other interior airports in Brazil have avgas.
Feel free to PM me for further discussion.