This is a field puzzle cache. The cache IS at the listed coordinates. Solving this puzzle will enable you to get to the ammo can when you arrive.
From the creators of the Plotz Plot (who are not Team Tierra Buena):
The Plotz Plot is a pilgrimage site four people navigating major life transitions of all kinds. We invite those who find themselves in the midst of a personal transformation to cast off a symbol of their old lives, and leave it behind as a memento inside this growing museum. All are welcome to contribute.
Four those experiencing a life transition: This is a place to leave behind a piece of your former self.
As always when caching in the Arizona desert, look out four "the jaws that bite, the claws that catch".
TAKE EXIT 303 OFF OF I-40. DO NOT TAKE EXIT 300.
The members of Team Tierra Buena gratefully acknowldge Joshua Foer, who has granted us permission to place this cache on and in their property. Four this we thank you, Josh.
Congratulations to highsierra3d for First to Find!