Your best bet would be to do one of two things, if not both of them: Call NLV police and get the info directly from them. You could also contact an attorney that knows that cities weapons laws.
As far as Boulder City goes, their city Attorney General has agreed that the State Premption does trump their weapon laws. You can carry your weapon freely just the same as you would in Vegas and no charges would be filed against anyone that is found to be in legal possession of a weapon. Again, verify this information yourself by contacting the Boulder City police station or their Attorney General's office.
I'm not exactly sure why NLV feels that they can still charge individuals with weapon possession but it is going to take an arrest of someone in legal possession of a firearm for a lawsuit to occur in order to get this issue answered and/or corrected.