Luggage and bags:
Try to keep as little amount of bags as possible. The more bags you have the more difficult it will be to keep an eye on them at the airport. I was able to pack for 7 days with just a backpack. It turned out to be very convenient.
Clothing/Shoes/Weather Gear: No need really for long sleeves unless there is some rain. Short sleeve shirts, bandana's, and shorts are probably most utilized. Sneakers are also good to have. Sandals are key because of the heat!
Toiletries and Medical Supplies: Hand sanitizer is VERY usefull!! It can be used anytime anywhere...A first aid kit is also a great idea.
Photo Equipment: a camera is KEY!!!! I brought my digital and did not have any problems. Took over 300 pics in 7 days.
Camping/Beach/Outdoor Gear: Make sure you check in to what beach you will be going to and if it is safe to swim there.
Miscellaneous: Bug spray and a bug net if planning to sleep at a non-inclosed area! Also I would reccomend bringing gatorade powder. Not only does it give the water a different taste, but it is a great way to restore electrolyte balance! Trail mix is also convenient to pack and is great for a snack here in there.
* Another thing that I learnt is to bring a twist cover water bottle, not like a "bike water bottle". This because if you have a fanny pack for the bottle or you are just carrying it around somewhere, the top you drink out of will become dirty by rubbing up against things (it is kind of unpleasant to drink out of after that). I recommend a one litre Nalgene bottle or any other bottle that is over 500ml (500ml was way to little when you had to go somewhere that didn't have water).
Good photo-equipment and films are very hard to be found for reasonable prices, and besides you will never know, wether the films were stored in the correct way.
So you better get enough films at home !
Miscellaneous: I bought many paintings of all sizes - and it was very hard to pass by any of the friendly young merchants without buying anything, as they all remembered well, that I bought a lot at other shops during my last stay - so why wouldn't I buy anything at them this time...
Miscellaneous: Pack patience! No joke..you're gonna need it...from when you get off the plane to when you get back on....