It was funny how much I read about what clothing to bring/where in Spain on various sites. First and most importantly I think it's blown way out of proportion. Common sense should prevail, comfortable clothes for site seeing and whatever else during the day and if you are having dinner at a nice restaurant then clean yourself up a bit.
Debunking of some things I've read.
"No one wears white socks, sneakers, shorts, t-shirts(especially with any kind of logos etc on them), or baseball caps." What a load of crap, what country are you people in? Agreed rarely will you see women in these things, even shorts, but men everywhere wear these things. No they are not all tourists because all the stores sell these items as well. They dress just the same as we do in the states, just different logos on the t-shirts and hats. And plenty of people wear jeans out at night to dinner as well. If you are dining on terraces etc, comfort was the rule of thumb. And you know what else? Except for a fine dining restaurant or upscale night club, nobody gives a rats ass what you are wearing. I mean c'mon they got better things to do with their time like enjoying the best sangria and gazpacho in the world.
One thing I never saw posted anywhere was how women/girls like to wear their pants, at least 2 sizes too small. Not a complaint just a very enjoyable observation, so women here in the states if you want to be Euro start wearing those tight pants or you won't get nearly the attention you deserve while travelling.