i doubt they'll have the powder shit at clubs. i just went to mexico city two months ago and nobody knew what it was. ecstacy and acid are the drugs of choice in the techno scene. cocaine and, of course, alcohol are the drugs of choice in the mainstream clubs.
if you want k, though, you can buy a vial at any veterinary pharmacy. you don't need a script and it's very cheap. i think it's made by ttokkyo, too.
you can then air dry it if you want, but i'd shoot it up!!
youll be in cancun...go downtown to a vet, i went to them they are everywere, and ask for ketemina. cook it on the coffee pot in your hotel room and sniff away my friend....good luck,