Hammocks Sold at Police Station

They must have to watch the inmates fairly closely as, I imagine, the materials used to make hammocks would make fairly useful absailing ropes, wall scaling nets and mantrap nets, and you could disable a guard quite quickly by wrapping them tightly in a hammock !

I expect that in Mexico. like everywhere else, work programs like visits and other privileges are something of a reward for compliant behavior. It's not impossible but I think it's more likely that unsociably dangerous felons would spend their time either locked down or doing less pleasant tasks. Hammock making requires a "shuttle" and no doubt some kind of edged device to cut the filaments with, neither of which would likely be trusted to an obviously risky prisoner.