I positively loved Moncofa and the apartment. Hector arranged a ride for me from the train station, which is about 5km from the apartment. Then a few days later arranged another ride for my sister.
It is possible to walk to the station, however, it does not have a ticket machine or window. A bus picks up near the main square, in front of the Moncofa boat 4 times per day (Hicid route - MONCOFA - CASTELLON) and travels north to Castellon de la Plana with a stop in Nules. A near direct walk from the bus stop to the Nules train station (exit the bus to the left, make first right and walk straight until you are at the station) takes you into Valencia (buy your ticket and there will probably be time for a coffee at the cafe).
The beach is a rock beach, but still lovely. In the month that I stayed the water was mostly calm and blue like the picture. My sister went to the beach several times and said that it turns to sand rather quickly in the water.
The apartment itself is great and as described. The patio is huge and you can see the water and the mountains.
The water heater broke one night and Hector had it replaced the next morning. So, five stars on responsiveness.
The town and its people are super friendly. There is a local market (in the off season it's not open on Thursday; credit card minimum is 10), tabac, bakery (open in the morning and weekends), a few cafes, 24-hour vending machines, and restaurants.
On Saturday there is a farmers market/ street market two blocks up from the apartment. The first street is clothes and household goods, the second street is fresh fruits and vegetables.
In the off season most places are only open on weekends. I highly recommend Campoy (go towards the beach, at Av. Mare Nostrum - the main beach road - turn right, it's the first restaurant), the food is amazing (in my opinion the best in town) and affordable.
In Moncofa you'll find several banks, supermarkets, a hardware store, an everything shop, internet cafe/mobile sim cards, and more. Walk along the main road into Moncofa (Av. del Port), Masymas is on the left (1 km) keeping going to the end of the road (0.5km), turn left, one street and turn right. This path takes you past everything I listed above.
If you're looking for a non-urban getaway this is the place!