Brazil is a great country. Rio is amazing but somewhat expensive. Actually the only thing I have really found that is expensive in Rio is the lodging. If you rent a place for a few months though I think it would be a lot cheaper. Plus the value of the real is dropping, so your money will go further.

Argentina exchange rate is 8.5 to 1 USD. You can bring case though and get 15:1 on the grey market. Something to consider.

On a side note. What do you do for a living? I've always wanted to work from anywhere in the world that has an internet connection.