Classes are Monday through Thursday. Classes start at either 6 or 6:30. What time classes end depends on the day, latest will be 9:45 or so, earliest is 7:30.
If you want a social life with students in your section, it's certainly possible. But it's still not like most people's undergraduate experience in terms of social life. Many of the 1E students are from/have lived in NYC for a long time, and are already settled in their social lives - several are married. Plus many of the students work during the day, and can't go out drinking every night.
That being said, there are plenty of 20-somethings who are fun. Pretty much everyone is friendly. If you want to, you can absolutely find an active social scene.
I'd say that most of the students are unmarried 20-somethings, but there is a sizeable minority of older, married students.
Everyone is pretty cool. There's very much a "we're all in this together" spirit, no tearing pages out of books in the library, or anything like that.