There is some excellent information on Marxuquera and the other crags that are in the region of Valencia on the website Valencia Climb. There are photo topos for some sectors, and the directions and general information is good and comprehensive.
On the way back we stopped where we should have on the way down, the Parc Natural de l'Albufera de Valencia. It is very beautiful, a strip of protected land sandwiched between the sea and a huge lagoon just south of the city, and felt like the only bit of coast that hasn't been 'developed' for the benefit of summer package holiday goers. We spent some of the afternoon on the beach and then followed the faded wooden paths through grassy dunes and tangled little pine trees to emerge at the lagoon. Lots of birds live there, big prehistoric cormorants and slender white terns and gulls, and hundreds of tall herons and egrets that prowl the nearby rice fields, and we watched them until we had to hit the road again. The drive back to Albarracin was slow and dreamy over the long Spanish roads, with mostly just the lorries for company, and music for narration.