Depends if you like the cold or not. Southern Brasil, which is more modern will be ALOT colder (single digits) and negative temps at night. But alot more to see ( this includes Foz- waterfall). The north has all the beaches and is warmer. Hostels are plentiful around Brasil and in a worse case senario, Ibis hotels are everywhere and for about 40 dollars a night. The cost would be getting to the north, Buses take way toooooooooo long, so finding an airline to go there will take some searching time. The main airlines are Gol, Tam, Varig (cheapest to most expensive). Foregt Sao Paulo as it is a business centre, not a tourist destination. If you are thinking of the beaches, Maceio, Natal, Fortaleza and Recife have good beaches for a major city,. Of course the better beaches are not in the city but there are tours going to other beaches for a cheap price all the time. Finding something cheap is alot more difficult or maybe someone else will read this and help ya.
[ Edit: Edited on 03-Jun-2009, at 08:46 by way2goeh ]