Maria is a very sociable and friendly host.
She was there before the trip to help us planning and during the trip when we needed her. She welcomed us and showed us her flat, and gave us some nice things to eat in the fridge. The appartment is conform at the description she made, it has everything you need. It is close to bus and metro station, and even by walk to the city centre. A direct bus line is aiming to the airport, 5 minutes walk from the flat. There are restaurants very close, some bakeries and 2 supermarkets.
We definitely had some great time in Porto and Maria was one of the reason.
Go for it ;)