Generally the Spanish public have not been presented with any arguments for why the euro was a bad idea. Furthermore the euro-sceptics were presented as being some kind of nationalistic lunatic fringe. This is not surprising since all the Spanish media chanels are incredibly biased one way or the other, and since all main Spanish political parties were pro-euro none of the media chanels had a reason to go “off message”.
From my various contacts with the Spanish education system, the Spanish have traditionally been educated the “old fashioned” way. That is pupils were presented with various bits of information and told to go away and learn it and then be examined as to how well they remembered it. There was very little discussion or debate and education was a one way flow from teacher to pupil. I know quite a few Spaniards who went to study in the UK and were surprised to be asked questions that had no straight answer, and which challenged them to creatively come up with their own ideas, present them, debate them and, if necessary, change them. This is gradually changing in Spain, but I think this lack of questioning of what you are being told still pervades through Spanish society and may be an underlying reason why there has been so little debate on the euro.