The apartment is so perfectly location in between the historic town, lower town, Pena Palace and the Castle. Its also right at the foot of the some of the major Sintra hiking trails just across the street from the information center. We walked everywhere. However the supermarket was a 20 min walk, partially uphill so you may want to grab groceries on your way into town if you have a car. Otherwise there is a tiny market offering only basics (no fresh fruit or veggies) in the historic center. On Mondays there is a farmers market within walking distance in the Sao Pedro area. Parking is tricky but Rita was so helpful with offering good suggestions for this. We went during Christmas so it was a little busy but I can imagine it being a lot busier in the summer months.
The apartment itself was very cute and cozy, and everything worked just as offered. There was plenty of hot water and the power never went out (in the past we've had many issues with the historic buildings not having hot water and power fuses blowing). There is traffic noise during the day however the bedroom is in back of the apartment and we didn't hear any noise at night. Rita had great communication and I would stay here again when visiting Sintra.