When we were in Miami a year ago, we took a Modern Tour of north Miami through the Art Deco folks (MDPL) in South Beach. The tour focussed on more transitional Late "Moderne" to early Modern, but they were very keen on preserving what's there... Also, as we drove around the city on our own - there were many modern treasures here and there. Fabulous Morris Lapidus work, the Bal Harbor mall is outstanding Mid Mod Shopping venue, the googie Banana Bungalow, charming roadside motels on the way to Fort Lauderdale and the penultimate tiki experience, the Mai Kai in Ft. L.!
I would contact the Miami Design Preservation League (MDPL) http://www.mdpl.org/
PO Box 190180, Miami Beach, FL 33119
It might take a few tries to find the right connected people there - but I know there are a growing number of Modern enthusiasts in that organization. Hey and when you find them - get Miami on the LL board to help with our mutual preservation outreach to the world!
While looking for the url for miami - i also found these guys: firstname.lastname@example.org
ADSPB 325 SW 29th Avenue, Delray Beach, FL 33445
Yah - they're deco, too, but there is a lot of crossover between the streamline and Modern - bet you'll find leads there as well...
good luck and please keep us posted on your progress.