Hi Loretta,
Follow the link to the big list of suppliers, many with online catalogs. Florida doesn't show any dahlia association sales coming up. The closest looks like it would be in Atlanta, but there are many people here who have ordered from various suppliers with complete satisfaction. No reason you can't do it too!
Good luck,
Poochella

Here is a link that might be useful: Dahlia Suppliers

You can order from any of the suppliers- they will ship when it's time to plant in your area --or earlier if you want to start them indoors or do cuttings.

Brent and Becky is excellent

A more updated list from the one listed 12 years ago in Poochella's post is www.dahliaaddict.com, which has a wonderful search/sort function by variety/form/color/size, as well as a current 'Taking orders in 2017' supplier list.

I just planted my first Dahlia..... In a pot. I only have apt. balcony.. do they grow well in lots?