Yes, y'all are that bad. Seriously, since I am still (dimly) able to rememeber being an 18 year old male myself, I do know what the temptations are in travelling to a country where drinking at that age is perfectly legal. However, I also remember what the consequences of indulging those temptations can be.

As noticed, most bars do not have a wide selection on tap. Asking for a "caña" will get you a (small) draft beer, usually Mahou in Madrid. My favorite is "Estrella Galicia," which is often available in bottles. It's sold in the US in some places, too. Unless you are masochistic, I would avoid a "clara," which is a small beer mixed with a lemon-y seltzer. Well, at any rate, I found it unpleasant.

Your best bet for meeting people your own age will be through your fellow students at the "instituto".

Have a great time. Do note that the Spanish way of going out differs from the American. Americans tend to hunker down in one bar and drink fairly heavily. Spaniards, on the other hand, will tend to walk from place to place, having a drink or two and a tapa at each place, often ending up at a club. Less conducive to getting wasted,as the walking and the food counteracts the alcohol, and more fun, in my opinion.

In general, too, Spanish girls (I'm assuming this is also an interest) are less tolerant of drunken foolishness than American girls. Many of my freinds who were fortunate enough to study abroad in Spain reported that the sort of drunken behavoir that is unfortunately acceptable at many American universities caused them to get made fun of by their Spanish friends. So, have a great time, but follow the Spanish lead in terms of acceptable amounts of drinking and behavior.

BTW, I thought the botellon phenomenon was mmostly restricted to younger kids? At any rate, I saw the aftermath at a park in Santander and it was really unpleasant.