You did the right thing submitting an ad to Ballroomdancers.com. When it gets posted, you will likely get a few replies. In the meantime, check the database of existing partners.
www.ballroomdancers.com/Classifieds/Partner/But don't leave it at that. Try going to competitions, posting ads in dance magazines like dancebeat, amateur dancer or the local usabda publication, and do a lot of social dancing at the local venues. If you have a regular coach or teacher, be sure to have him or her keep an eye out for you and pass the word around the dance community.
Good luck with your search!
Sincerely,
Jonathan Atkinson