We arrived at the apartment past midnight and were initially taken aback to find lots of folks hanging out on the neighboring streets which are lined with bars. However we were quickly reassured by Maria, who kindly handled our check in, that Porto is incredibly safe - a fact which proved to be through during our entire trip. As our room faced the backyard, we did not encounter any noise issues from the bar patrons. However, do bring ear plugs because the church bells nearby ring every hour throughout the night. Also, we left the window upon as the room doesn't have ac. While the temperature was perfect, there were a couple of mosquitoes so we had to buy some repellant.
These minor annoyances didn't take away from the apartment's perfect location. We walked everywhere without much trouble as the city was incredibly easy to navigate. Maria also offered great recommendations such as a chic fresh seafood spot Ostras e Coisas just up the street (do make an advanced reservation or pop in early for a table).
The small apartment was also very sufficient for our needs, and Paolo was also kind enough to assist with making a restaurant reservation for us prior to our arrival :)