We stayed at Marco's place for a week. We didn't meet Marco in person but met his mother in law Cassilda who was friendly and gave us plenty of tips and information about Porto. The flat is in a good location, not far from the metro station. There are many great cafés, bars and restaurants nearby. You cannot hear any noise from the streets, though one of the neighbours was playing their TV quite loudly until about 1am most nights, so if you're a light sleeper you may want to bring ear plugs just incase. We had a good stay overall and enjoyed our time in Porto.