I live in the Las Vegas area (Henderson, Nv) and dutifully check for the signs before entry. I carry in several casinos without issue.
However, about three months ago I started playing poker on Wednesday mornings at the Eastside Cannery casino. Not seeing any postings, I continued to carry while playing. Last week, I was leaving the casino and happened to see a small, metal plaque on the side wall between the inner and outer set of doors clearly stating that no firearms were allowed.
Clearly, I had been in violation. However, the location and size of the plaque (there was also one on the opposite wall about 75 ft away) had been a factor in my error. So, my "lesson learned" is to really scrutinize large entryways before entering.
Needless to say, I leave my gun in the car now. However, I discretely mentioned it to another regular player who carries as well. He also had never seen the sign and he's played there for two years (since they opened).
I also play a lot at Sunset Station. It's a large complex with movie theater, bowling alley, and a daycare facility that is not marked with "No Firearms" signs. However, I was concerned because of the daycare facility and asked the chief of security about the situation. He told me there were no firearm restrictions because the daycare facility is at the far end of the building.
Ignorance is no excuse.