As for showing the Fat Cats of the world that they are ***king the **it out of people... dont bother... there are plenty of Brasilian's working on that, have been for a long time... the problem is not a lack of evidence, the issues are MUCH MUCH MUCH more entangled than that. Indiference, and more importantly, greed, market pressures, and a general cultural mindset that says "this is just the way things are" are the primary culprits in the situation.... No amount of photos will make a difference, only legal or market pressures will change the way things are... if your images can cause a change in legislation (which, with all due respect, is not likely, as there ARE plenty of people with their feet on the ground there right now working on it), or bring to bear some kind of market pressure like sanctions... a mere boycot wont do **it . . THEN yes, I'd focus on the conditions... but unless you already have a contact that is willing to push your photos into the right venues.... you'll be far better off looking at the people, than at the sewage.
Like I said - if you can find a party that has some clout, and they are willing to mount a campaign around the pics you take - something like a show in Brasilia (the Capitol), or an ad campaign that targets the CONSUMERS of particular Brasilian products (SUGAR!) like CokaCola... then.. and only then... would pictures of "economics" be most advantageous...

All the above is only my opinion Donald, and I'm not particularly sure that any of it should bear on anything you will be doing.. for after all, the trip is yours, the camera and film are yours, and in the long run, what you do or dont do is NOT up for some decision by committe.... take it all as simple opinon, and of course, you'll draw your own conclusions...

In no way do I feel that ANY kind of photographic work done in any country should be curtailed. I do however opine that there are forms and forms that can suit various purposes.