I try to make an annual trip down to the keys(my only real vacation), and there are a ton of great spots out there.
One place that I would suggest to check out is The Bahia Honda State Park. Now that might be a little drive from where you are but it definitely has flats and channels. I'm hoping no one here considers it their sweet spot, it's well known. But it has proved successful for me on the incoming tide for bonefish (I have yet to land one) and I have seen tarpon cruising the channels in the evening. Permit is kinda a myth IMO on those flats as I have never seen anyone actually land one, but people at the local bars will tell of stories of big ones.
Definitely grab a map though as there are tons of put outs all along Route 1 through out the islands. If you are fishing from shore, and decide to fish the bridges, bring some grain lines to get down as the current can rip through there. I have had some great success with grain lines in ripping current.
Also on Marathon I believe, is The Island Fish Company. great bar, a little pricey, and they have a web cam there.
A GREAT breakfast spot around there is the Wooden Spoon. It's a great place for an early morning breakfast and a box lunch. Usually they give two sandwiches a hard boiled egg a bag of chips and a coke for like 6 bucks.
Good Luck and tight lines!
Alive without breath,
As cold as death;
Never thirsty, ever drinking,
All in mail never clinking.
- Riddle