A few friend and I traveled to Valencia (following our La Tomatina camping experience) to Barcelona a few days ago and I wanted to share a few details you might find valuable.
First of all, the cost of the trip — the regional express that leaves at 17:00 is the cheapest train we found for 24.50 Euro. We arrived at 22:00 at Barcelona Sants station.
Second, a quick tip for buying a ticket in the Valencia train station — if you are buying same day tickets (we had no problem getting a ticket end of August, but could be different if buying in extreme high season), then do not get a number and wait in line with everyone else. We wasted 30 minutes waiting before we figured out there is a booth at the far left of the Renfe ticket area that is labeled “Salida Hoy” (Leaving today). Go to that line and just buy your ticket; the numbers are all for people buying advance tickets.