I would highly recommend staying at Federico's place - his apartment is located in a safe, quieter neighbourhood within walking or metro distance to all of the attractions! We found that there were plenty of good food places nearby (within at least 500m-1km) but the neighbourhood was nice and quiet. The room and apartment are clean, tidy and we felt very comfortable. We didn't have much contact with Federico but this didn't bother us at all as we were happy doing our own thing. Thanks for having us Federico! We'll see you next time :)