
You can find a short version describing competition dance tempo guidelines here:
http://en.wikipedia.org/wiki/List_of_DanceSport_dances
For the actual rulebook check here:
http://usadance.org/dancesport/forms-and-resources/rules-policies-and-bylaws/
and download the 2012 Dancesport Rulebook.
Both of these are in measures (bars) per minute. Here is one converted to beats per minute which is what I believe you indicated in your post.
http://www.superdancing.com/tempo.asp
If you can dance cha cha at that tempo and maintain technique good for you!