while safe `n sound is good at muffling ambient noise, it doesn`t deal with vibration noise, ie footfalls that travel through the joists due to people walking (or in this case dancing). Now since the dance studio is below the apts and your concern is noise travelling up not dance shoes over head, vibration may not be as much of a concern but, from what I`ve been told if you do want to deal with vibration noise the best way to do that is by creating a dropped ceiling. Friends of mine build sound proof rooms in their house as they had a music school and what they did was creating a box within the existing walls. That way the sound vibration did not travel into the next room through the studs. If you go to websites on soundproofing, they will discuss this phenomenon more in depth, but basically the way to stop sound from travelling is by not attaching the new ceiling to the old ceiling.
There is also a special fire/sound reduction drywall that has metal in the middle, it`s supposed to be as effective as putting up 8 sheets of drywall, very expensive, unfortunately I can`t remember the $$$, nor the name of this product, did see it being used on an epoisode on "holmes on holmes" once, so you may be able to track it down that way.
From my personal experience with safe n` sound, my guess is that it won`t be sufficient on it`s own to deal with the noise from a dance studio.
Terri.