I agree with Bandit here. Meth should be legalized. I imagine the number of meth labs would probably decrease since it would probably no longer be as lucrative as it is now.
Although you are quite correct that the problem of meth labs could be cured overnight by legalizing it, I just don't know if it should be made available in stores. The same thing with Heroin, PCP and perhaps Cocaine. These drugs are just too destructive or addictive imho. Of course all criminal penalties for possessing or using these drugs should be rescinded immediately.