They have such an ability right now. They could easily get a fleet of quarter scale R/C aircraft with autonomous control ala pixhawk, load them up with explosives and fuel, and send them on a one way trip to the big city. Maybe $5-10k ea. The first attack would likely be very successful, because nobody is ready for it. Expect effectiveness to degrade over time as air defense systems and fighters are deployed.

I wouldn't expect them to do this, though, because anyone contemplating such a thing would realize the response would be immediate and decisive. Cartels are after all business organizations, and you can't do business if you're spending all your time dodging hellfire missiles.