They told me it would be 4 weeks before I heard from them, but I think it depends on when you are there. The admissions committee meets once a month (if I remember correctly) and I happened to be there right after they met.
It's been a little over 3 weeks since I interviewed with them and I haven't heard anything yet.
Good luck to you. I felt like I had a really crappy interview at another school, but they accepted me anyway...you never know!