Stayed in Jose Diego's apartment for 4 days this December. Apartment was very clean, nice bathroom, good size bedrooms, fairly comfortable bedding, TV with english channels )) lounge was large and nice. Had 2 friends visiting with me and everyone was pleased. Kitchen fully equipped with everything, we cooked a dinner on the Xmas day and didn't lack a thing for that.
The flat is very close to the city of Arts and Sciences, 5min walk, the area is safe enough, and apartment is a 35min walk from Central market, and 15min walk from Russafa and Gran Villa with their restaurants and pubs, 20min from the main shopping streets and squares, so we never used public transport and walked it all about, just fine.
Finally, communication was fine, although I did feel a bit nervous that I only got the details of the address when I was already in Valencia, but it all turned out okay. Easy check-in, easy check out.
I recommend Jose's apartment and himself as excellent value for money place to explore valencia and himself as a decent host.