Prostitution is a problem in a wider area than Nevada, if you were here in London, you will see how big the problem is just by using the public phone service
Just because it is "safe" in Nevada, doesn't necessarily mean it will work elsewhere. Prostitutes in Nevada aren't like Eastern European girls being duped into prostitutes against their will. I don't think legalising prostitution will make the problem go away, rather make the problem worse
How, exactly? If given a choice, I think people will choose to go to prostitutes regulated by the government. Thus driving illegal prostitution out.