God I feel stupid to not know where it is, but where is this BMX track you guys speak of? LOL, I live in the East End and go down Williamsburg every day and have never noticed it, but I'm also not a very observant person (unless I'm trying to be).
I do know a small course we used to play on when we were kids. It's been at least 10 years and it was on private property I believe, so you may not want to go there. But it is a pretty neat little spot with a lot of nice jumps all crammed together. LOL, nevermind... I was just trying to find an address using google maps and I used the street view to get the clostest address... when I came around the corner on the map it appears they have tore that entire spot down and it's a construction site now