Flying in to Cancun from the US in a couple of weeks. Are you supposed to declare any jewelry you have on you?
If you are going to be wearing it with the tags still on, they might get suspicious, specially if you are wearing 44 necklaces, 21 bracelets and 5 rings in each finger and toe. I personally wouldn't bring anything of value since most of the time I'd be half naked. Maybe my laptop and a good camera, but nothing to let anyone know my social status. Nobody cares anyways, exept for crooks, transitos and customs.
No you don't have to decalre anything going into the country. I think unless it is alot of money something crazy like over 10 grand or so. I think it says that on the Customs form you fill out on the plane
If you have over $10,000 cash on you the you must declare it. There's some other things too but none would apply to the typical tourist.