The Lemon Tree House is great! Is cozy, comfortable, clean and spacious. The kitchen has everything you need, the bed is comfortable and the garden is amazing. It's close to the subway, but if you feel like it you can walk to the old centre (20 minutes). There are supermarkets, bakeries, shops and restaurants nearby. Linda and her husband were very helpful and communicating with them was easy.
Would definately recommend this place and this hosts when visiting Porto!!