welllllll, I LOVE Rivera Maya! I highly suggest doing the local favor. There are many things that would make for a wonderful favor that is traditionally Mexican.
1. Biscochitos/biscochos- these are a Mexican styles sugar cookie that is made with brandied anise, and rolled in cinnamon sugar. YUM!
2. Tequila is a common thing that is made in the area. If you are okay with alcohol, maybe finding individual sized tequila would be the way to go! OR have someone set up a tequila tasting stand instead- I am sure guests would love it, and it
would make some great memories!
3. There are always fun local little "tourist" gifts, from flip flops, to woven bracelets, to little handmade dolls. You could have a variety, and set them out randomly at place settings.
4. Are you musically inclined? Traditional insruments like maracas and castanets would be a fun way to showcase your abilities, and give them a way to play with the beat of the music at your reception!
5. I have to mention, sombreros! The also made mini ones, and these could fall in the tourist type gifts mentioned earlier.
There is so much you could do! :D If in doubt, talk to your wedding coordinator at the destination site for more ideas. They would love for you to support local merchants, and probably even know some! :)