Mexico's best charro horsemen, wearing traditional wide-brimmed sombreros, lassoed galloping mares, flipped bulls by their tails and tested their mettle atop spirited horses on a recent weekend in Mexico City. It was a national tournament of the country's official sport: charreria, or Mexican rodeo. The sport evolved over centuries from the demands of working life on ranches. The skills and traditional dress on display in charreria evoke a bygone…