Uh, Grogs, where in your review do you mention . . . the authentic Mexican locations? You may not believe this, but a Western filmed in Mexico has a more interesting look than those innumerable ones shot at Spahn Ranch. And the Morricone score is better than you make out. The location shooting and the music alone lift this film above most other American Westerns of the period.
A film is not significantly improved by simple virtue of its locations, anyway. It's how they're used.
It would be nice to see Boetticher's original screenplay of this.