I've attached a link to the FL Native Plant Society. You should be able to search for native nurseries in your area.
Marion

Here is a link that might be useful: Florida Native Plant Society

As far as spacing, maybe consider Dwarf Firebush. Firebush enjoys a variety of lighting conditions (constant shade will make it stringy).

The Dwarf variety is not about the width/size of the plant but about he leaf size. The leaves are about 1-2 inches x .5x1inch compared to a standard firebush 3-5 inches x 2-3 inches.

It is native hardy and a moderate to fast grower. Does well in containers. Should be able to find at any nursery. NuTurf in pompano sells the dwarf variety (nuturf is a franchise I know in miami).

A great place to go is Flamingo Road Nursery, the employees here a very knowledgeable and the nursery is fantastic.

I have it near my pool and have no problem maintaining it at a nice bushy 2-3 foot high and is always flowering.

http://www.flamingoroadnursery.com/

Here is a link that might be useful: Flamingo Road Nursery

Thanks linchat! Question though- I read that the dwarf varieties are not native- have you hear this as well?

Yes, I've heard that the dwarf variety is an African Firebush which is being passed on as a Florida native and is making the native firebush harder to find. Also, the African Firebush is spreading on its own, posing a hybridization risk with the native plant.
If you want to take a day trip, Indian Trails and Meadow Beauty are two native plant nurseries in Lake Worth. Also, Garden Gate at Sears in Pompano supposedly has some native plants.

Regina

Here is a link that might be useful: Firebush

Thanks for the firebush info regine and the other nurseries- looks like what I am going to have to do.