I'm also from Rio, and have visited Recife a couple of times, although it has been a looooong time ago...

The advice you've gotten from Andre is particularly apropos.
"City of God" is a decent look into the lives of Brazilians. Also, Xingu, and "Behind the Sun" (it's native name is Abril Despedacado"), Pixote, Dona Flor and her Two Husbands is another classic from which you can draw alot of assumptions about the place, and it's rhythms.

As with any country that has one foot in the first, and one foot in the third world, the scene is VERY complex. There is another facet that I personaly find interesting - there is dignity, happiness, and humanity beneath the scab of poverty - not only in Brazil, but in any place where people are under alot of durress... that is what I'd be interested in showing... not to exalt the conditions (which are deplorable), not to sidestep the issues, and not to parse a warm fuzzy over a situation that is raw and rough... but really to talk about the people, and not so much about what ails them. What ails them will unmistakeably show thru in the environment and surroundings.. there is no escaping that.. but the when and who you frame and shoot can show so much more than a disection of economic factors...
I can asure you that somewhere along your trip you will run across a bunch of children, probably barefoot and wearing only tattered or no shirts, playing soccer in a street lined with garbage and possibly an open sewer... and I also guarantee you that if you stand there for five minutes you could pull five images of jubilant faces grinning under the sweat of exercion.. THAT is Brasil.... Brasilians are a people that deal with their tough conditions with a heart full of levity, and an eye for the simple joys of life, despite all else...

If you can capture that juxtaposition, you'll have gotten something beyond the cold outsider's perspective of "this place is poor", and have gotten at the heart of what it means to be poor, but unbeaten.

GO MAN! I guarantee that you will come back inflamed at the circumstances, and if you really get it, a little in awe of the people who manage to cope and find happyness on the margins of a larger economy.