A big issue in using cc in Spain Is unrelenting Dynamic Currency Conversion. Many local cafes and similar shops have processing machines that automatically run transactions through in dollars if the card is US. Then the merchant acts dumb and suddenly loses all English skills.

In a Toledo lunch spot, I refused to sign the receipt unless the charge was re-run in Euros. The man behind the counter laughed, threw the unsigned receipt in the register and went on to the next customer. Sure, you can deny the charge with your bank, but how much time are you going to spend to get 60 cents back?

i just started using cash for smaller purchases and saved cc for hotels, real restaurants and larger stores. Attractions were all ok with cards.