Everyone's made great suggestions for both clothing and shoes. Keep in mind that it will be humid as well as hot - 100% cotton or rayon or rayon/linen blends work well. Be sure your tops do not let in the sun or always put sunblock EVERYwhere before going out in the sun! Once I took a "slinky" knit top and found that after a day outside I had a "tan" made up of hundreds of tiny little tan spots where the sun shone through the tiny little holes in the knit!!
I always take broomstick skirts and 3/4 sleeve or short sleeve cotton knit or rayon/blend tops. I find that in the summer, pants (even loose legged) are just too hot for me. OTOH, as Bea Farhana said, they have beautiful skirts there at very reasonable prices - shop the downtown clothing stores.
Make sure your skirts you wear on the street will not show the outlines of your legs when the sun is behind you! Either take totally opaque skirts or take a long cotton half slip to wear underneath. If you buy a skirt or two there, they will be opaque.
...and - HAVE A GREAT TIME!!
