I'm confused... We've done a Eurail pass, long, long ago. You used it to get on trains. It was easy. Apparently, in Spain, the pass isn't enough, you need reservations, for limited 'pass' seats - and the reservations cost more money. How do I learn what the 'real' costs are for traveling in Spain/Portugal with a train-pass?
You should be able to get train fares on http://www.renfe.com/ for Spain and www.cp.pt for Portugal. You could also run your route through http://www.railsaver.com/ I didn't bother with a pass for Spain and Portugal - just bought tickets as I went. Also, don't know your route, but Renfe doesn't run trains along the north coast of Spain, a couple of private companies - Eusko Tren and FEVE - do, and they probably wouldn't take the pass.
Thank you, I'll try those.