I did mine back in the ‘90s at this place: http://issvalencia.com/ It’s a block off of c/ Blasco Ibáñez, right around the corner from the UV facultades. Courses are typically September to December, and January to April, and the school can make arrangements so that you can get a pensión arrangement in a private home. Last I remember, their US office was on the West Coast, San Francisco perhaps? Anyway, they operate an English school as well, at c/ el Bachiller 13, and you can look them up on Google Maps as “The American Institute.” to get a feel for the area. Valencia has quite a few choices for such schools, including an exchange program through the University of Virginia that allows tag-a-longs from other institutions. Good luck with your search.
ETA: Wow, holy thread necromancy, Batman! I just noticed that I disturbed the rest of something from 2012. Hopefully the info will do someone some good anyway.