Real legalization would see it grown commercially on private farmland, just like everything from corn to peanuts is grown on private farmland. The illegal operations on public land we see today would not be profitable, and so would stop.
As long as the government didn't impose truly draconian taxes and regulations, there is no way that the illegal growers could possibly compete with the legitimate ones. Cartels and the guy on the street corner would be out of business. Moreover, the licensed dealers would not jeopardize their license by selling to minors, or, if they did, they'd soon be out of business. There would be more control than there is now.
So, unless you enjoy being a part of that 5% of the world population that is supporting 25% of the prisoners, you really need to look closely at legalization.