I have a couple of ideas in mind that needs clarifications because they are repeated insistently but not fine-tuned and I think people are getting the wrong impression:

1. It is NOT desirable to be late in Spain, not 5, not 10, not 15 minutes, not anything. It is NOT funny, it is not enjoyed, it is not appreciated, it is not considered a virtue or positive trait and it IS plainly rude. The average Spaniard will look at their watch, and say «I am sorry, I am late, have you been waiting for long?». The answer will be: «no problem, it is OK» and they will move on. The fact that Spaniards take their life with a laidback attitude and are not easy offended doesn't mean that it is socially accepted as possitive. Don't ever entertain the idea of being late to a business meeting, or to school. Not a long time ago when, I went to school, being late for school could mean punishment. Being 5 minutes late is not considered a positive thing but it is not considered super offensive either. So, do not confuse terms that can put yourself in an unpleasant situation. Beware.
2. When you go to somebody's house, it IS not positive (again) to be late but in this case, the «social rule» is very lax. They will be less annoyed than If you were late at a meeting point like a café or restaurant. Again, don't do it or don't look at the time because somebody has told you that being late is welcome in Spain. It is not, but it can happen and they won't take it personal. In any case, we are talking about 5 , 10 minutes…
3. Unless you know how to speak spoken Spanish AND (not or) understand the pragmatics of the language, always say «thank you» and «please», especially «please». In casual situations, coloquial Spanish works as a tonal language. Yes, Spaniards don't say it that often but that doesn't mean that it is not implied through other linguistcs mechanisms. If you say: «give me some coffee» you have to do it in a certian way. You see, in Spanish “please” and “thank you” are a lot more implied in the speaker’s tone or in the way we construct words rather than stated explicitly. Do it wrongly and you will be killed with a gaze.
4. Queues are important. Jump the queue, and all hell will break loose. Just try. Now, somebody said Spanish queues were chaotic, well yes, they are not lines of people standing up, but a group of people standing close each other. So you need to ask «quién da la vez?» or «Who is last?» when you want to join the «queue». It is considered offensive if you don't respect the queue. Young people will tell older people that «I was first» with no shame and nobody will get away with it. Respect the queue.