Best way to maintain gardenia bushes

I can't offer much personal experience, but I trust Cooperative Extension folks, and your FL CE folks have this handy guide for you: http://edis.ifas.ufl.edu/mg336

Beth, they are an acid loving plant and an enriched soil is the way to start. The soil must be well drained, and they are a heavy feeder so small doses every few months in your dry sandy Florida soil will work for you. Another feeding schedule might be better for plants in other states as the climate and soil is different. They are fine as a potted plant too. They love used coffee grounds, chelated iron Azalea/Gardenia food and Epsom salts. Florida soils are extremely porous as a general rule so feeding is the key as well as an even moisture level.

Rebel- do you have to protect them from afternoon sun in Florida?

I believe some of the biggest mistakes with most flowering ornamentals come from improper maintenance. I see over and over Azaleas or Gardenias trimmed at the wrong time of the year, most Azaleas and Gardenias in Florida should not be trimmed after August, any trimming done past August will remove the flower buds that will be opening in the spring. As important as not trimming past August is to PRUNE one the flowers have finished, this pruning after the flowers have finished can be from 20 to 40 percent this will keep the plant thick and full and aids in low maintenance. As for the sunlight required I love to install a Grafted Miami Supreme Gardenia I have used this plant in full sun to 65 % shade

You would be surprised to see how many mow and blow guys out here prune Azaleas and Gardenias into meatballs. Then the homeowner asks me why the don't bloom. They just figure the guy with the chain saw knows best.

This answered my questions, but what will happen if coffee grinds gravitate to bird of paradise?

Off the top of my head, they should be fine. My dad threw coffee grounds on them, roses, and anything else in the path.