First of all: I spent 10 days at Lurdes place and it was perfect. The kitchenette is kind of a garden house in the backyard, with camellias and lemon trees, chickens and two dogs in a kennel. So you shouldn't be afraid of dogs and maybe have a flashlight for the night. But having said this, you couldn't expect nicer or more helpful hosts. First thing I got was a city map with all personal highlights (which was very helpful), and we had a lot of nice talks during my stay.
As for Porto: it became one of my favourite cities. Mostly, I explored everything by foot, it's about 20 minutes from Lurdes house to the river Douro, and the main metro station, Trinidade, is about 5 minutes from Lurdes home. So you can reach her house easily from the airport.
All in all: my best recommendations!