I was married in November at EDR. I grew my hair out nice and long for a year and a half because I really wanted to wear it half up, keeping the length hanging down my back. Although everyone I talked to said to wear it up - at least then I know exactly what I'd get vs. something that falls. I went down to Mexico with two inspiration pics - one an undo, the other a half-up/half-down style.
Once we got to the resort, I realized it was pretty windy on the beach, and that an updo was going to be "it". I had my hair rehearsal for the updo, and loved it. She then restyled my hair so it was more of a half-up style since we had our welcome dinner that night. That's when I really came to terms with the fact that the half-up style would drive me CRAZY in the wind.
On our wedding day, it was even more windy on the beach. I did the updo, and my veil still blew off 3 times (I didn't secure it as much as we should have).
I'd highly suggest having both an updo and a half updo in mind. Then you can check out your ceremony location once you get there for the "wind factor". And of course you'll know how humid it is and if you end up like Monica...
You can always do a TTD or day-after shoot and have your hair down later.