I was doing a tree inventory project at IpBio Iporanga for two weeks with my girlfriend and was very satisfied.
The facility itself is located in the very beautiful reserve in the forest, which was very refreshing after Sao Paolo.
There are variety of projects for people with various backgrounds, however, some projects require longer stay.
Our project involved marking, measuring and preparing data for identification of the trees, so we were able to spend a lot of time in nature (which is amazing here!!)
We were also able to see projects which other volunteers were working on - like researching local frogs, tadpoles, luminescent mushrooms ( they are super cool! ) and audio monitoring of the forest.
Since reserve is located in nature - get ready for the local birds, you will really see and hear them a lot!
One thing that I can definitely recommend is learning some Portuguese beforehand. While some members of IpBio staff speak English, so there's no problem during the stay, you will feel quite limited in communication on the way to reserve, as well as during traveling around on your own.
The kitchen they currently have is a bit small if you have other volunteers around, however they are constructing new building right now so it should improve soon.
The staff is very helpful - they helped us to arrange interesting activities (hiking, going to caves etc) for the weekends, as well as figuring out transportation afterward and other practical questions.
If you are coming in winter definitely grab some warm clothes, it can be really cold at night.
I can definitely recommend this place, and I'm looking forward to checking out some other centers they plan to open in Brazil ( especially in Amazonia).