just another opinion
A great deal of my flight time (limited as that is) is flying in that part of the world. It is possible to make the trip safely, but, BUT (big but), it is more likely that it will end in tragedy. This is a part of the world with 6% of the world's avaition and 46% of the world's fatal aviation accidents. I disagree with the poster who said that it is not rocket science. Maybe I am slow and stupid, but as a military aviator flying turbine powered equipment I found myself challenged everytime I went flying. There are many grand adventures to be had in aviation. This one is up there.
The challenges (incomplete list)
High terrrain
Lack of radar coverage
Unreliable Navaids
High terrain
Open Water
Billingual ATC
High terrain
Incomplete radio coverage
Host nation search and rescue
Terrible weather
Improperly Terps'ed charts
- if you don't know what this means you have no bussiness flying down there
Suggestions
Bring someone who knows the area
Bring GPS
Bring someone who speaks Spanish
Bring someone who speaks Portugese
Fly day/VFR into large airports ONLY
Avoid Colombia
Avoid Peru
Avoid the Andes
Avoid the open water
How about doing that Belize trip first? It is a lot shorter, involves fewer countries, avoids high terrain, and will definatly give a feel for some of the challenges flying south can provide. If he can't find a copilot I have some free time (unemployed) and I can help him with the experience and Spanish speaking suggestions

- but I would't go with him to South America until we did a "practice run" to Central America and back. In fact, even having "been there and done that" I would want a practice run for my own benefit.