If you are looking for Aztec gold, as opposed to Mayan gold or whatever, study Aztec history, not fantasy magazines. There may be gold buried in Southern US, but it won't be Aztec gold. It is pure fantasy to think the Aztecs mounted an expedition of hundreds of miles through enemy territory to bury gold in Arizona, when they owned a major part of the Central Highlands of Mexico. And, during a time when they were dying like flies from smallpox, and fighting to the death. The Aztecs were simply not that stupid.
Some of the local legends, such as Moctezuma eating fresh fish from the ocean every day when he visited here, have been found true. They had runners who constantly ran. Go to the top of the Volcano by Orizaba, take insulated baskets of ice to the ocean, mix it with fish, and run the fish here, like relays. This was part of local legend, and has been affirmed by history studies.
Another one, that in Tenochtitlan, they knew within hours that the Spanish ships had arrived. Turns out the Aztecs used mirror signaling and the word was passed in a few hours from Vera Cruz to Tenochtitlan (Mexico City now).
Many skeletons have been found buried in the area. Since the church was up and running in 1620 (documents available from the Latter Day Saints) and after that all would have been buried in church cemeteries, those skeletons are very old.
The only gold known to be discovered here was a neck piece on a skeleton found in the floor of the house, now a ruin, my wife lived in as a girl. it was donated to the church to buy a new bell. her grandfather said that was in 1911 when he was a young man. Dates here are not reliable; older people often can't even tell you when they were born. The new voter's system means that will no longer be true.
People have dug and dug with no big treasure found so far.
Cortes said much of the gold he didn't get, fell in the lake and was lost during the fighting. I believe him.