My wife and I really enjoyed staying with Sueko & Mafalda. They were very understanding having to wait for our check in due to a late flight arrival into Lisbon. Once we met up, they spent considerable time with us explaining the neighborhood and the great sights to see.
Regarding the location... the Alfama location is a great location to see the city. If you have to go further than walking distance, the flat is near the Santa Apolonia Metro stop and we used it often.
Great food, great sights... Hope to be back in Lisbon soon!