We would have to legalize all illegal drugs, not sure I am willing to do that...even then criminals are involved in much that doesn’t involve drugs...completely legalizing marijuana would have an effect but there is too much other crime on the border and in the inner cities for it to be a cure.
If marijuana had not been criminalized to begin with I think things would be better today, I don’t think the whole “war on drugs” would have had support. I could be wrong but that is how I see it.
The one consideration for legalizing weed to deal with the cartels is that they still make a majority of their money off the weed. If you legalized weed they would still smuggle coke, heroin, meth (remember when that was made in America?), and people. My guess is that they would make up the difference by fighting over territory and taking over all human smuggling. Depending on how bad the new immigration bill is, that might be a huge business opportunity for them. Controlling routes, coyotes and even the issue of ag worker visas on the Mexican side.