Re: 2 questions about New York City - drinking age and whats on!
There are a lot of places in NYC, and other places in the United States that will let you into their venue if you're 18, (or sometimes younger), but you won't be allowed to drink.
The Bitter End is like that. I saw Oz Noy there, but I didn't think I'd be able to because of my age.
Other places just won't let you through the doors. My cousin and I went to see Teddy Krumpel with Shawn Pelton and Mark Guiliana at Rockwood Music Hall and the bouncer wouldn't let us in. We still got to watch/listen from outside, but as you can imagine, that's wasn't much fun in the New York September..
I would check out the website of specific clubs/venues/restaurants before planning the trip.