Tried using the RENFE site and have being hard time understanding the results I'm getting since it's in Spanish. The site is not very user friendly non Spanish users. Can someone give me a rough idea how much the round trip ticket is from Madrid to Valladolid?
This will depend on the date you want to travel and the speed of the train.
There are step-by-step instructions in English at http://www.seat61.com/Europe-train-tickets.htm#How to use the Spanish Railways website.