updated May 29, 2023
Nevada is one of 45 open-carry states, which allow private citizens to carry visible weapons without any license or permit (long guns are a different story). Fifteen states require some form of license or permit in order to openly carry a handgun. Five states (California, New York, New Jersey, Illinois, and Florida) plus the District of Columbia, prohibit the practice entirely.
In Nevada, anyone 18 and older who can legally possess a firearm may openly carry virtually anywhere in the state that's not specified, as below.
The state of Nevada prohibits carrying (either openly or concealed) weapons on the premises of a public school, college, and university or a child-care facility, including in the parking lots, unless the carrier has the written permission of the college president, school principal, or head of a child-care facility. Open carry is also disallowed in state legislative buildings or wherever the legislature is conducting business.
Federal facilities where open carry is not permitted include courthouses and offices (like a Social Security office), on military bases (military personnel should know Department of Defense policy and individual post orders), USPS property including parking lots, and VA hospitals/facilities/cemeteries.
In Nevada, Hoover Dam prohibits all firearms.
Red Rock National Conservation Area disallows loaded firearms (no magazine/clip inserted, no rounds in the chamber).
As for private property, guns-prohibited signs on private property do not have the force of law. You can legally carry even in establishments that advertise you can't.
However, if the owner or management asks you to leave or disarm, you must comply. If you fail to do so, you can be arrested for trespassing.
Private-property owners can and do prohibit open carry and most gun owners respect the right to private property (in the same way that they respect the right to bear arms). The ones who have a problem with being unarmed in places that don't allow open carry simply don't frequent them.
Private businesses in Las Vegas where visible guns aren't welcome include, but aren't limited to, Sprouts, Buffalo Wild Wings, Ethel M Chocolates, Red Robin, Raising Canes, most malls, and most casinos.