We let the Marriott know ahead of time that I was a Celiac, and Executive Sous Chef Dominic Esposito got back to us right away reassuring us. He was true to his word. I was so well taken care of, between gluten free pancakes to pasta to other meals, desserts, and yes even gluten free breadsticks!
I actually found out the chef was making separate meals for me (we stayed at the Club level at the JW) when he left a message about a lunch he wanted to deliver -- but we were off property. The next day, gluten-free pancakes showed up at breakfast! We were out of the hotel for the rest of that day, but my meals were totally covered from thereon out, although I insisted they didn't need to do anything for breakfast since there was always fresh fruit.
Lunch/dinner included sandwiches, GF pasta, steak, a shrimp dish, dessert plates consisting of cookies, cornbread, and muffins, and the biggest salad I've ever seen with the most incredibile gluten-free bread sticks. It was awesome, and I was blown away by how seriously they took the Celiac issue, how hard Chef Esposito worked to educate himself beforehand and the lengths he went to in order to get food stuffs -- including flying the pasta in from Mexico City, and getting gluten-free soy sauce from another hotel!
His care and attention made sure the trip was a success and I left Mexico vowing that if I ever went back it would be only to the JW or Casa Magna Marriotts (which are right next door to one another and seem to share executive talent). The beach is gorgeous, the JW's pool is one of the most spectacular I've ever seen, and the GF food was awesome! If you are a celiac or have other food allergies, check out the Marriotts in Cancun!