I had a really nice stay in Gian Lucas' apartment, it's very bright, you have a really big and sunny terrace! Communication wise everything was perfect.
The location is a big plus, right in el Carmen, the old town and close to the Turia gardens. A great tip is to rent some bikes nearby and go explore Valencia by bike (Ciudad de las Artes y las Ciencias and the coastline).
The only negative point was that the neighbors were a bit noisy and the matress was a little too hard for me.