I am doing the Camino in June. and will be flying from Santiago de Compostela to Madrid then continuing to Castellon de la Plana. My question is would it be easier and or less expensive to fly from Madrid to Valencia or rent a car and drive.
I think it will be less expensive to take the train from Madrid to Valencia.
You can get from Madrid to Valencia in 1 Hr 41 mins. via AVE ( high speed) train.
From Valencia to Castellón de la Plana you can take a train that takes about 45 minutes.
The Spanish Railway website is : http://www.renfe.com
You can also check this website to compare different transportation options: http://www.rome2rio.com
Edit: I forgot to mention that above trains run hourly.