From Orlando the closest salt fly fishing is out of either Titusville, or Cocoa. The Indian and Banana Rivers, both salt water estuaries offer Redfishing, Sea Trout, Jacks, and a few others to keep you busy. The best areas for wading would likely be the Indian River out of Titusville. Head over there, cross the bridge and causeway out toward the National Seashore, take a left at the Y, on the major highway Ying off to the north, once you leave the water, and then once you get to an arched bridge crossing a large waterway you've arrived at DIY wading central.
Coming back toward Titusville on the left you'll see an old weather station and little road, that goes back and edges southerly along Mosquito Lagoon finally ending up back on the National Seashore access road. Fish the canals and wade cautiously as some of the areas along this side of the Lagoon are mucky. Once out to the National Seashore go down past the parking lots till you see the sign for a boat ramp on your left--back in there the wading is firmer and you are on the Ocean side of Mosquito Lagoon.
Now back to that humped back bridge or Haulover Canal, -coming back toward Titusville you'll find several roads to the right through old orange and grapefruit groves that lead to the Indian River and wading. Primary targets for all these places are Reds, Black Drum, Sea Trout, Jacks, and Ladyfish. There are also lots of neat birds once you get back in the vicinity where the road Ys off from the National Seashore Access road. It's the Black Point Refuge and everywhere they build a road they dug a canal and the canals have fish including young Tarpon and Snook.
If you can do it a wise move would be a half day or more with either John Turcot, Mosquito Lagoon Fishing Guide
or Eric Perez east central florida, orlando & mosquito lagoon fishing with Capt. Eric Perez
as both are very knowledgeable fly fishing guides and your time will be well invested.