The only instruction sheet left in my room at the Colegio Mayor Cardenal Cisneros told me about meal times and following that was a warning in four languages (Spanish, English, French and German):

Our visiting professors are kindly requested not to stay in short trousers, swimming trunks or tracksuits in common areas of the Colegio Mayor. We appreciate your collaboration.
Visitors must be received only in the lobby or in the Bar.