Technically, no. The possession of it has been decriminalized, but it is still illegal. Buying, selling and transporting it are still offenses that can result in arrest and criminal charges.
The decriminalization aspect applied largely to personal cultivation and use for spiritual reasons, out of respect to locals and their spiritual beliefs.
Tourists to Jamaica often find that marijuana is easily available for sale as soon as they get to the island, and if caught smoking it, the arrest and fine is usually a hundred American dollars, which some users just see as a cost. Trying to take any of the drug home however is still highly illegal, both in Jamaica and most home countries.