As many cultural phenomena are generational trends, eating ass has been normalized by Millenials and GenX. Taking a trip down to Mexico means to lick somebody's asshole.
Faded buddy 1: "Eat ass? dude, not me.."
Faded buddy 2: "What's wrong with taking a little trip down to Mexico?"
Me: "After our first date I took her on a trip down to Mexico! And you know what?? We fucked all summer"
(Girl getting back to her table at "Riley's" bar):
Friend: "I saw you come out of the bathroom with that guy... Was he helping you yak?"
Girl: "Nah, he just took me on a little trip down to Mexico!"
An interval of reminiscing about all of dabuxom chicks who have allowed you to "pleeze squeeze theeze" in years gone by.
Horny dude: Wow --- not to brag or anything, but whenever I musingly take a trip down Mammary Lane, I always feel really good about myself dat I was able to be so kind and gentle and charming dat I actually succeeded in wheedling da underwear off of so many hot babes; guess I can also give myself a pat on da back dat I also managed to keep my head and was responsibly careful during said delightful romps wif all of those blinky-eyed cuties so dat I never got any of them pregnant, especially since dat's often NOT da case for guys who have intimately communed wif dat many "willing" females.