The only problem with legalising drugs isn't that everyone will start using them, or using more of them. It's the government getting greedy and thinking they are the only dealer in town, upping the price, and then the cartels just go out there and undercut them.
The government is always at the heart of the problem. If organized crime becomes more engaged in competing with other sources like the government, it's much better than their entire focus being reserved on violence. Law makers are the gate keepers and I wonder how many more innocent lives it'll take for them to admit their wrongs.
Here in Canada I am legally authorized to carry 5oz of weed at all times because I finally got my medical pardon. That's a quarter pound, dude. But somewhere in the States it could land me more prison time than if I had raped someone. That's just because of how the laws are. The actual substance is far less dangerous than prohibition.
Now you have these crazy ass cartels. That's a whole different beast. They're a product of their environment too though. One of the best strategies would be to legalize drugs. Mexico is a shit hole anyway, so lets use this as a social experiment and see what happens. I predict that it'll bring their revenue down substantially. Any time law enforcement tries making a move, these guys shoot a bunch of innocent people in broad day light to show that life means nothing to them. I think this is pretty much the only move they could make without being put back in checkmate again.
I don't know what else could help Mexico. Poor fuckers are FUCKED!