I do highly recommend Maria´s apartment if you are planning to visit Porto.
It is a very cosy apartment full of nice small details. Location is good, not perfect, but you can easily get to all places by walking around. If you do not feel to walk you can access the metro in a few minutes.
Maria is very nice and is always available. She gives you the best advice on what to do and see. And we were welcomed with a nice bottle of wine with a nice message on it :)
Obrigada Maria!!!