If you're an adult, there are no states in the U.S. that require you to wear a helmet on a bicycle. There are a handful of liberal, nanny-state towns here and there across the fruited plane that do.
None of them are in Nevada.
I guess when a state has taken care of its crime, educational problems, and welfare costs, it can turn to pressing matters like helmet regulation. But rest assured that if a helmet law does pass in one of the fifty states, it's going to be in some place like CT, NY, CA, or NJ. It's not going to happen in Nevada.