We loved our time at Cinco (Carole's place). The view is stunning, the gardens are lovely, and the space is welcoming. Carole is an accommodating host and was able to give us tips on getting around. The location is quiet but a very short walk (less than 5 minutes) to the main square in Sintra. We especially appreciated the fresh oranges, bread, homemade jam, yogurt, cereal, coffee, and tea for breakfast!
One note that the roads closest to Carole's place are quite narrow. Our rental car company ran out of small cars so we were stuck with trying to maneuver a large vehicle. I don't mean this as a critique as Cinco, but more of a suggestion to insist upon a small rental car or possibly take the train to Sintra if you're coming from Lisbon.