This is unrelated to the question (sort of) but I googled Corky Ballas and found corky dot com. I was reminded that his dad, George, invented the weed eater! I knew that from years ago but hadn't thought about it in ages.
Unfortunately I couldn't find any contact info for Corky on the sight. But the pictures are fun to look at.
As far as I know, Shirley Ballas lives in England, and travels extensively, by invitation, for coaching, judging, etc. So she doesn't teach at any one place in particular. She arranges to teach a certain person, or group, at a convenient location. Since NYC is a place with many dancers, she is frequently there. When in NYC, she could be found at any number of studios, depending on the person(s) she is teaching. As far as I know, she is not associated with any one place. In other words, you can't just go to one of the studios suggested above and expect to find her, or ask to see her. [Unless she happens to be there, by chance.]