Possibly the best possible location in Lisbon! Very close to Rossio station, super central, lots of cute coffeeshops and restaurants nearby. I'm also a runner and enjoyed being close to a couple different running routes -- Lisbon in general isn't a great city for running, but there are a few routes and Carla's place is well-located for that.
No locks on the doors for the individual rooms, and there are other guests. It seems safe enough, but people who are sensitive about security might feel a little uneasy.