We stayed one week in this appartement (couple and 3-year old) and can really recommend it. Quique was very friendly and helpful. The apartment is spacious and located perfectly. Just between the old town and the beach. A busstop in front of the door and a supermarket just across the street. Metro at about 5 minute walk. With the bus you can be on the beach in less than 15 minutes. We also rented bicycles at the hotel Marina Atarazanas (where they also provided a childseat free of charge, bikes where €2,- per hour).
Valencia is a great city and we will definitely come back and will stay in this appartment again!!!