We initially had thoughts of climbing Camelback Mountain in Ajo to see this cross up close and personal. Unsure of the conditions and property ownership, we asked Mike, our host at the Guest House Inn, if it would be possible to climb to the cross. There's no trail that he is aware of, he said, and he had climbed it himself, but not since he was a kid. Looking at the size of the mountain and considering the hot (100°+) weather, we decided against it.
On our final morning in Ajo, as we were driving around searching for the Ajo Visitors Center and mine lookout, we caught a very good view of the cross from Santa Ana Road, just off Indian Village Road. Actually, the sign at the nearby residence says "Greenway House"—perhaps it is still in the family? It's directly across Indian Village Road from the mine lookout, as we eventually discovered.
See http://www.cunews.info/greenway.html for more on John Campbell Greenway. The article mentions the cross erected in Greenway's honor on Camelback Mountain.
Recovered in good condition.