When will you be there? I am going from June 11-18 in Islamorada. We have had little succes in all our ventures.
If you fly fish bring your gear, you can always get a guide and go out, they know the area really well.
If you're bringing your boat and its not for the flats I wouldn't recommend messing around as you may get stuck.
Send me an email and I can discuss more. I have been there 3 times and this will be my 4th.
Hope to hear from you soon,