There will be alcohol and parties on every floor, some moreso than others depending on the people. Not wanting to be surrounded by parties isn't exclusive to Muslims, so no, it's not primarily Muslims (or any other group). I didn't find it to be any different in terms of student background than any other floor.
Not all Muslims choose not to drink or party either.
There tends to be less drinking and whatnot on the non-alcohol floors, but some of the people who choose these floors simply do so because they don't want to be surrounded by parties all the time, and sometimes people get assigned rooms on designated floors even though they didn't choose it, just because all of the other rooms were filled up.
Like James said, people won't try to force you into drinking - for the most part, people are pretty respectful. You might come across an occasional jackass, but that's just part of life
Partying doesn't necessarily equate to drinking. I've been to many parties where I didn't drink - I'll typically have water or sometimes orange juice. It's nice to socialize with people, and I was never pressured to drink. But if you don't want to socialize that's fine too - there were some people on my floor that I almost never saw.
Just as others don't typically try to force you to drink, you can't force people not to drink. You should be aware that there will be alcohol in every residence building in every university, and if you're not okay with that, then residence probably isn't a good option for you.
