<<Disclaimer: Verify this information before applying it to your situation.>>

Thanks to all who sent ideas and support for travel to Cancun, Mexico. What surprised me most perhaps was how much people really love Cancun, returning time and again to enjoy it (e.g. 10 and 15 times). The posts total about five pages, so I am just giving a skeleton summary of the relevant information:
No airline can get it right; Only drink bottled water; AAA had a few nice gf meals; great luck with Delta airlines; American Airlines only messed up once in 20 trips;Very easy to find gf food in Cancun; the staples are beans, corn, potatoes and rice; they do not have pasteurized milk; be careful in cheaper places where they might use canned sauces, premixed spices, etc.; Mexicans would not have hidden rye or oats in food, but maybe barley; if you want cereal, take it with you; tamales, enchiladas, mole sauce, salsa, chile sauces should all be gf, also flan (egg custard) or even dulce de leche (sweet caramel made out of sweetened condensed milk), helados (ice cream), ice milk (horchata made from rice, flavored with watermelon, banana, mango, etc.); be sure to ask for TORTILLA DE MAIZ (corn tortillas), and avoid the flour tortillas; melon, kiwi and papaya are very popular in Cancun; make an ART OUT OF PICNICKING - a bag of goodies, local market for fruits, cheeses, drinks;STICK WITH BOTTLED WATER AND DRINKS, hotel ice is supposed to be okay, but several mentioned the non-celiacs even getting Montezuma's revenge (diarrhea)- excellent advice to boost probiotics before the trip and take some with each meal while traveling; take the restaurant card in Spanish (from the book Against the Grain, or try http://babelfish.altavista.com translation service); We stay at the Royal Resorts in Cancun - Royal Sands, Royal Mayan, Royal Caribbean and Royal Islander. It is a time share - you can rent a room, suite or villa - the food and beverage manager is very helpful - even makes a gf pizza;The Marriott also can accommodate you on food; the renaissance hotels are part of Marriott www.marriott.com, and have two properties in Cancun - very helpful - send off emails asking banquet managers what accommodations would they make, and have the email in hand when you go; Adventura Hotel has a restaurant with a menu instead of buffet - was able to eat most of the stuff and was very good, breakfast and lunch at the buffets not difficult to stick with simple stuff; Continental Villas Plaza Hotel was not too accommodating, but their ribs restaurant bbq sauce is gf by CSA/USA standards; "IF YOU CAN GO ANYWHERE IT IS CANCUN"; (others actually suggest Rome to be on the safe side gf-wise, especially since you can buy gf snacks at all pharmacies); go to http://forums.delphiforums.com/celiac/messages for the folder on Travel and Abigail's gf food, product and medicament list; Restaurant called Tres Amigos is very good (tacos, corn chips, tostados), stay away from burritos (wheat based); Planet Hollywood has good steak dinners; Chichen Itza tour is a whole day and great - lunch is authentic Mayan cuisine; Wednesday afternoons is the day for bullfights; Evening cruise ship dinners are fun - brisk ride on a pirate ship on the gulf, or gentle ride on the bay.

I'm still not certain how people feel confident just looking at buffet food and knowing it is gf (even the melon might be cut on the same board as the bread, it seems to me, or the same gloved employee might be piling the stuff into the serving trays), but I very much appreciate the good information and the time people took to share it. I hope this summary will be helpful to others as well.
Hilary

*Support summarization of posts, reply to the SENDER not the Celiac List*