I've always felt that Ride Vaquero was one of the weakest of Robert Taylor's westerns. In playing Rio, Taylor certainly essayed one of the darkest characters he ever brought to the screen.
It's the end of the Civil War and bandit Anthony Quinn has certainly had his run of things in the area. But the Yankee army will be occupying Texas shortly. Common sense would dictate that Quinn realize the jig is up that he'd better move on. At least his foster brother Taylor thinks so, but Quinn is drunk with power and he ain't going nowhere.
Taylor finds some reason to stay when he takes one look at Ava Gardner newly arrived in Brownsville, but with husband Howard Keel. They're settling on a cattle ranch and Keel has some big plans.
Most of the story I got, but quite frankly two points of it were ridiculous. Why Keel would even consider hiring Taylor after Taylor tried to burn him out. And secondly why Ava had Taylor take her to Quinn's camp to convince him to leave her and Keel alone. Those two things make absolutely no sense at all.
Quinn is repeating the blustering role he had in Viva Zapata. But that film had a lot more depth to it. I think Quinn realized that and blustered all the more.
Other reviewers commented on the undertone of a repressed gay crush that Quinn had for Taylor. It certainly might explain Quinn's motivations. But Anthony Quinn dealt with that issue six years later in Warlock, a much better western.
It's a bad script with character motivations that make no sense. Still a good cast does the best they can by it.