What are the best iPhone data plans in Portugal and Spain?

I will be traveling in Portugal and Spain (attending the OFFF 2009 Conference) and would like to use my unlocked 2G iPhone to check email and check Instructables. I am currently an AT&T subscriber, but their international data plans are too expensive -- $.0195/KB or so. Are there providers in Portugal and Spain that will allow me to buy a month's worth of unlimited data usage for a reasonable price?