Don't misunderstand me. That stereotypical idea of Spain being the country where everything is done "mañana" is false. You don't get to be one of the world's leading economies by being lazy. But when the day's work is done, then meeting with friends over a copa or two is pretty normal. And when it's party time, believe me, the Spanish know how to party!
The man who coined the phrase about New York being "The City That Never Sleeps" had not been to Madrid. It is quite normal for working hours to go on until 8pm, so at a time when the English or Americans have finished dinner and washed the dishes, the evening in Madrid hasn't even begun. It's pretty usual for me to meet friends at 9 or 9:30. For Friday nights make that even later! And the only reason many evenings finish around 1pm is because the Metro closes at 1:30, but there are always plenty of taxis. In the centre it's pretty easy to party through the night. This is highlighted in the way that Spanish actually has a verb that means "To party through the night and go to work/school the next morning without having been to bed": Empalmar. (You have to be careful using that verb. It has another meaning if used reflexively which also means to "stay up". I will say no more!)
An often quoted statistic is that Madrid has more bars than the whole of Belgium. Someone once told me it was possible to go to three different bars each evening for a year without repeating. I would say that's a conservative estimate. Visit La Latina, Chueca, or the area around the Puerta del Sol and you will never be short of somewhere to drink. A thought that would gladden the heart of any English binge drinker. BUT, binge drinking is alien to the culture. A drunk is a rare sight - and, I am sorry to say, probably English. I am sure that the sight of a pack of Brits on a stag or hen night brings golden euro signs to the eyes of bar owners all over the town, but those of us that live here tend to avoid places with such groups. The gutters of Madrid are not filled with vomit night after night. It is not considered polite, or "bien educado" to be drunk in public. It is not considered macho to be so. And one's friends do not put you down if you choose to have a coffee or chocolate instead of that last beer. Although the "one for the road", known here always as "the PENultimate"(!) is an oft used phrase.
You can get beer in pints, but mostly one drinks a "Caña" - a beer of less than half a pint usually served with a small offering of food: a plate of olives, potato crisps (chips in the US), a variety of "tostadas" (small pieces of bread that are only sometimes actually toasted with a savoury topping) or slices of delicious Manchego cheese). And you can drink a lots of cañas in an evening. Favourite brews are Mahou and Cruzcampo, but the Irish pubs sell Guiness and Murphys etc. Several bars specialise (if that's the word) in many beers from outside of Spain, or different regions of the country. There is definately no lack of variety.
The residents of Madrid are friendly. There are no lack of friends with whom you can have a night on the town. But you will lose them if you get drunk and start a pub brawl. Civilised drinking - how refreshing!