We had a great time staying at Maria's apartment. It really is central--we were able to walk everywhere and only used the bus when we went to Belem (which we would've needed to do no matter where we stayed). The apartment was supplied with everything we needed, including a fan to keep us cool at night. The apartment is in a quiet area, which was nice to come home to every night.
Maria was out of the country during our stay, but she was easily accessible the entire time. Her friend was the one who met us and let us in. He was mixed up about which day we were coming, so no one was there when we arrived. But the moment Maria found out she fixed it immediately, and we had access to the apartment within 40 minutes. No complaints!