@Zoological Point I'm not sure. The snakes signed in the area are:
Arizona Black Rattlesnake Crotalus cerberus
Mojave Rattlesnake Crotalus scutulatus
Santa Catalina Island Rattlesnake Crotalus catalinensis
Mottled Rock Rattlesnake Crotalus lepidus lepidus
Great Basin Rattlesnake Crotalus oreganus lutosus
Sidewinder Crotalus cerastes
Cantil Viper Agkistrodon bilineatus bilineatus
I think it might be the Santa Catalina? The sign has a photo of both a dark one and a light one, like this snake is.
