"...four or five shots of tequila, and then another shot. .." That's a lot of tequila. I'm not saying they weren't poisoned but they could have just been drunk and dehydrated and jet lagged. That article is a little sensationalized, written with some generalizations; however, I've never been to any of the places in that article, so I shouldn't comment, but. ..
We've been twice, LOVE Nachi Cocum! Highly recommend! They can make money charging so little bc Mexico is a poorer, developing nation, and tourism is one of the most important industries to their economy. Why would they intentionally poison people. Doesn't make sense.
Been there twice, too, love it there, too! Was a sleepy town, now they're really trying to rebuild a lot of resorts. Would def go back.
Also, the all-inclusives they're citing in that article are not the all-inclusives you're speaking of for port excursions. These, they try to please day trippers so you come back and write good reviews, tell your friends, etc. I'm not sure what they would gain by poisoning you.
Who's to say, though. Sad stuff in that article.