Hi Angie,
I am not too familiar with So. Nevada but have heard that the "Lake Mead National Recreation Area" is OFF LIMITS to all treasure hunting, detecting included. Possible Confiscation of your equipment and fines if caught. I believe they won,t even let you coin shoot on the beach.
The area you mention might be inside the border. Extractor and a few others on here live in southern part of the state and they could help you more than me. Hopefully they will chime in here and give you some good info.
HH
Steve