Hitchhiking in Brazil (Rio de Janeiro)

Hello all,

Me and my sister are soon going to be in Brazil (beginning of April) Hurray!!!
We are going to spend there around a month. We were considering hitchhiking, as a way to travel, but I heard and read some kinda scary stories :( Anyway, since I don't believe maria much, I wanted to ask what do the people who live there think? Is it a good idea? and Is it doable?

Thank a lot :)