I've never been to a party like that, where loads of people I barely know get drunk. The only parties I've been to have been small occasions, with a handful of friends. I don't think I'd much care for the type of party that people here are describing.
The only sort of 'party' that I've ever walked away was my end of school formal. There was lots of loud music so nobody could talk to each other without yelling, which to me seems absolutely idiotic. So basically I ate my meal, sat around for a while straining to hear people, then finally gave up and told people I was leaving. The event was a total bore and a big waste of money.
About alcohol, I do not personally like the taste of it. I certainly do not drink it around other people, for fear of doing something really stupid (which has happened before with very bad results). The only time I drink it is when I feel really down, which of course is a bad idea. But generally I do not even do that anymore (at least, not for the last two years).