I stayed in Rosarios apartment for a conference at CPBS. The location of the apartment was therefore perfect (7 minutes by foot). The apartment is simple, but absolutely sufficient and practical for this purpose - and I slept very well :) The surroundings are great with a beach within 2 minutes walk.
Rosario is a very nice host and took care that everything went smoothly. E.g., I arrived in the middle of the night and the check-in worked out nonetheless without any problems.
If I travel to Porto again, I will certainly consider staying in this apartment again :-)