All in all we had a great time in Porto and enjoyed our stay at Maria’s house. We had no problems communicating, although we never met Maria in person. Our room was great and very comfortable, unfortunately the common areas (bathrooms and kitchen) were not as clean, as we expected.
Getting to the city and the port took about 20 - 30 minutes, as the house is a little further away from the center, but due to the metro getting there is no problem.