I really enjoyed my stay in Luis' apartment. His son came over to let me into the apartment at the time we agreed and communication was very good.
Luis' apartment is on the 2nd floor of a building in the heart of Bairro Alto, which means that most of central Lisbon is within walkable distance. There is a primary school across the road (which means it's a bit noisy during the day on weekdays) and a small bar next door, which was only a bit noisy on Saturday night. Overall noise levels could get quite high but I was able to sleep well, as I'm not fussy.
The flat itself is very spacious and open, it could easily sleep 6 people if needed and provides a shower room and open kitchen. For me this flat provided excellent value for money and I would definitely recommend it for the location and accessibility to restaurants, bars and nightlife.