Yes, you are correct in that state laws protect your right to openly carry there.
The local governments of The City of Las Vegas, the City of North Las Vegas, and Clark County are KNOWN violators of the state preemption laws and state CCW laws. They will illegally enforce whatever damn rule they like. Our state's preemption law against this has no penalty clause.
If you are willing to be the test case, go for it. I expect you will be hassled and informally trespassed. If we are lucky, you will be cited and/or arrested so that we may start the court proceedings against them.