It's amazing how hard it is to find a bright yellow snake. They're supposed to be poisonous, but they're real mellow, so you don't need to worry about getting bitten unless you start poking the snake or picking it up.
Mexican West Coast Rattlesnake (Crotolus basiliscus) by Kai Rösler. A venomous pit viper species found in western Mexico. The specific name is derived from the Greek word for king, basiliskos, and alludes to this snake's large size and potent venom.