Someone like Taylor Hawkins doesn't need to go to Colombia to get drugs, he'd get just as good stuff at any big hollywood party.
The reason they're there is every big band does basically the same South American tour. They all play Rio, Sao Paolo, Buenos Aires, Santiago, Bogota, Lima. Usually they time it to hit the big festivals which end up having almost identical lineups from one week to another in Chile, Colombia and Brazil.
Those are going on over this month and why Foo Fighters and a bunch of other bands are in South America right now - The Strokes are doing an identical tour.