:) Most people drink to all hell on the weekends, but are studious during the week.
There are lots of activities that people can do and usually people to do them with.
Carleton is definitely not a dry campus and while alchohol is the drug of choice, there's a good amount of pot use and a very small harder drug scene as well as a good number of kids who don't drink (I'd say about 10% don't drink at all and another 20-30% only drink very small amounts infrequently).
I didn't drink almost all of my freshman year and never had trouble finding things to do.
There are also activity buses that go a few times a term to plays, movies, and other events happening in the cities, so don't think you'll miss out on those things!
It's pretty easy to get your own bus to go to an event, as long as you invite the whole campus.
If it was this year I'd probably gotten distracted from sleep by a conversation with my roommate about some strang facet of international news (he loves to find humorous news about obscure parts of the world), talking with the girl across the hall about our Muslims in Modernity reading, or playing guitar hero with my roommate.
One big Carleton tradition is Heaven and Hell, a dance party held in Evans dorm on two levels so one room is "Heaven" and one is "Hell." Everyone dresses up and gets sorted to one or the other, but you can move between the two freely.
If you're not into partying, there isn't pressure to participate and there's plenty of other things going on.
The campus does have a bit of a work hard party hard atmosphere to it.
People generally withhold drinking/partying until the weekends since there's usually too much work before then.