Posted signs at the entrance to Gov owned/operated buildings, child care facilities, and school/university have legal weight and you can not legally carry within those buildings.
Las Vegas Convention Center is owned/operated by Clark County Gov. Which means you can not carry within the convention center.
Casinos are private property. Posted signs have no legal weight. Which means you can legally carry within. But, if you are discovered carrying, they can ask you to leave the property under NV trespassing laws. Therefore, keep it concealed.
From personal experience, if hotel/casino security discovers you have a firearm they will do one of the following:
1. Ask you to leave.
2. Ask you to secure the firearm with them (hotel/casino security).
3. Ask you to secure the firearm in your vehicle.
4. Ask you to secure the firearm in your room.
5. Ask you to keep it concealed.