I highly, highly recommend these people: http://www.rioholiday.com/Rio-Holiday-Experience.htm
The owner is American and the beach houses they rent are amazing and within an hour’s ride to Rio. They provide transportation and a translator. Very nice people. We stayed in one of their houses in fall of ‘07 and it was one of the most incredible vacations of my life. We were totally taken care of. If they are booked up, I’m sure they could steer you in the right direction of where to stay and how to get around. I can’t say enough good things about these people. And they were not expensive at all. Everybody on the trip felt like the whole experience was a huge bargain. And everyone agreed that if we ever went back, we would use these same people again!