As this article from Budget Travel points out, flight passes within a country or a region often sound better on paper than they work out in practice. In all my years of travel, I’ve only bought a flight pass once–when we planned to cover a wide swath of Indonesia and the Visit Indonesia pass ended up saving us a few hundred dollars.
In too many cases, however, they’re a bust. I looked into the Argentina Airpass before going down there this summer and the price the airline quoted me was actually more than the price an agency quoted me for just buying the flights individually. And the latter didn’t come with a bunch of rules. The South America pass might make sense if you were visiting three or four different countries, but you really have to pore over the terms and do the math.
And this is in countries where there is very little competition. If you are going to a continent where there are plenty of budget airlines running, it rarely makes sense to buy an airpass from the legacy airlines. You’re better off winging it when you get there or getting tickets through the budget airlines that run on the same routes. Start with whichbudget.com to get an overview.