First and formost you need to bring an open mind and a willing heart. This retreat experience can and should be a life changing event. Leave the "contempt prior to investigation" in the drive way at home.
Material items to bring;
Sheets and pillow case covers for a twin size bed, larger ones work just tuck them in.
A towel to use for showering.
A chair - beach folding chair or a "bag" chair will work just fine. There are benches in the outdoor chapel but some prefer a chair for morning meditation.
A flashlight - the grounds are well lit, but you may need to get into your luggage in your room at night without waking your room mate with an overhead light.
Your Big Book and 12&12…. Why would you leave home without them?
Bug Spray - It is usually cool enough that bugs are not a problem, but better safe then sorry.
Warm clothes - There is usually a chill in the morning and evening at this time of year. It can get into the lower 40s so be prepared. You should also check your favorite weather web site for the Tampa Bay area.
There are canoes available for free time on Saturday, if you plan to canoe bring a set of clothes you can get wet, must have closed toe shoes to canoe.
Rain poncho or rain coat, Florida weather in the fall can be wet!
One nice outfit - You may be asked to speak and if you are we would like you to dress up a little as a sign of respect for the podium.
A friend - or several friends. This is an experience you will want to share with someone. The drive to and from the retreat can be another fulfilling aspect of the journey.