The common name would be "vira-lata," the formal term would be SRD or sem raça definida (without a defined breed).
My guess is you already know that the dog is a mongrel. I saw this movie again recently and got a good look and found a picture of a dog very similar to the one in the movie. It also comes from the Brazilian favela where Ed Norton/Bruce Banner lived in the first part of the movie. In the review below centering on animal oversight by the Humane Society, the dog's breed was never mentioned, probably because it is apparent that it is a mixed breed.
ahafilm.info/movies/mr.phtml?fid=7936 no longer exists
picasaweb.google.com/calaplant07/BrazilFavelaTour#5107544886667487714 no longer exists
The name that they have given for these stray dogs, mostly of mixed breeds, is "vira-lata." It translates to "turn-can," referring to the pitiful practice of these abandoned animals (the term also applies to stray cats) of having to overturn garbage cans in search of food.
http://eyesonbrazil.wordpress.com/2008/04/25/vira-latas-no-place-to-call-home/
http://books.google.com/books?id=XXsIB1s1YLMC&pg=PA465
http://books.google.com/books?id=XXsIB1s1YLMC&pg=PA476&lpg=PA476
There are many other pictures out there of these "vira-latas" in the favelas of Brazil, but some are just too difficult to look at. Life seems really hard in those favelas.
https://en.wikipedia.org/wiki/Favela
