Possible Clues:

• Toledanos talk in it
• Language close to portugués
• Opening screen option on many an A.T.M.
• "Lengua" on a peseta
• Local language error keeps on returning
• Latino's language
• Daddy Yankee sings in it
• You'd hear it in Toledo
• What un crucigrama is in
• Plácido Domingo sings in it