The organization of the meeting has got discounts on prices of some hotels in the area. See the list here.
Due to the proximity and convenience, the organization of the meeting suggests accommodation at Hotel Everest (in the list).
Clube dos Macacos (http://clube17.com.br/)
It is a pleasant club 5 minutes walk from IMPA. It will offer complete meals and drinks (inclusive) at the cost of R$ 15.00 (students) and R$ 25.00 (professionals). The reservation for entrance and lunch in the club must be made in advance with the local organization of the event due to the limited number of places.
For more information about Rio de Janeiro, visit Visit.Rio.