Would legal drug use cause more people to use drugs? If you use Portugal's example, the answer is, "no." Humans are very predictable. If you tell us we can't have something, we want it. The US uses alcohol less than most other developed countries, but during Prohibition, there was an insane demand for alcohol. Since we have Portugal's successful example of what happens to a country that legalizes drugs, we have our own Prohibition to draw upon and the massive problems with the cartels just across the Rio Grande, I think one evil is less dangerous for society as a whole.