new york blows for stop and go riding. i actually hate it sometimes. you can't do serious training on the surface streets here - it just ain't going to happen.
slvoid said it best - go over into jersey and ride in the palisades park. nice and hilly leading up to a .90 mile climb at the end. then you can just stay on 9W for as long as you want. the next best (i think) are the two main parks - central park and prospect park. you can ride without stopping there and you'll always see other riders.
remember - george hincappie came from new york. he must of found places to train.