Hang out in the shade. Even with a high spf and in the shade you will tan. A severe sunburn can quickly ruin a trip.
I've never been down south, but my co-worker does and she always buys a few facecloths at the dollar store and brings them. She say they sometimes run out by the time they clean your room (depending on where you are on their run) and you don't always get some or enough of them. If she winds up having to use them, she leave them there and doesn't worry about bringing them back.
Now with the airports and weight restrictions on luggage, you want to leave a little bit of wiggle room for your luggage weight. You're going to a tropical area which has higher humidity, so realize that the very same luggage will weigh a bit more on the return trip because your clothing has absorbed some of it. It sucks being hit with a surcharge.