I think it should be legal. Marijuana has a lot of medicinal benefits, and it shouldn't be illegal just because a small minority choose to abuse it. I don't use marijuana, and I'd rather not be around people under the influence (by that, I mean I'd rather avoid them while they're high, not avoid them in general), but I think that if people want to mess with their brains like that, they should have the right to do it. Alcohol and cigarettes are legal, and they do far more harm than marijuana. Besides, we already know Prohibition was an epic failure, and even though alcohol was outlawed, people still secretly drank it, much like people still secretly smoke pot.
I also think legalizing marijuana would improve the economy. It would introduce several new markets (both medicinal and recreational, not to mention all the things you can make with hemp), and the government could tax the everloving shit out of it. I do think they should impose some legal restrictions, similar to alcohol and cigarettes (no selling to minors, no driving under the influence, etc.). But it would also free up police forces, who could put their services to better use, locking up serial killers and child molesters instead of relatively harmless druggies. Besides, it would also help calm the violence with the drug cartels along the border.
But legalization is probably years away... a lot of people are going to resist it, and you're going to see mothers telling their sob stories about how they lost a kid to drug use and bla bla bla... (Look, if your kid did drugs in the first place, don't blame the drugs, blame the kid.) In any case, keeping it illegal just contributes to the problem.