I had a lovely stay as a solo traveler visiting Lisbon for the first time. The flat is situated on a side street in Bairro Alto and is accessible via metro at Restauradores. I stayed over a weekend, and while the street can be festive, I did not find it disruptive. At ground level, you really feel part of the atmosphere of the fun neighborhood.
Although the flat is compact, I appreciated the large bathroom and separate eating and sleeping areas. I would definitely recommend this place to other travelers!