I also ran last year, Valencia is a lovely city, really easy to get around. The marathon is flat & not too crowded, there's a brilliant atmosphere around the course, with plenty of drinks & gels handed out. The expo is easy to get to and a 15 min walk from nearest metro.
I travelled on my own & stayed in an apartment 10 min walk from the city centre. Supermarket & pubs nearby. & metro stop 2min walk away. They were called 'valencia central apartments'
Doing the French Riviera marathon this time, but will definitely run Valencia again in the future.