Although decriminalized, ganja is not yet widely available in Jamaica legally.
Medical and Sacramental shops are currently the only legal ganja options.
There is a legal place for buds in Negril. Milo has set up a Rastafari sacramental shop on the cliffs, the Lion's Lair at Banana Shout.
Pretty much everything else you may run across in Negril is still illegal. At this point is probably best not to mention anybody's names...
