Cut lime lengthwise in half. Cut one half into 5 wedges; set aside. From uncut half, squeeze 2 tablespoons juice. In pitcher, mix Bloody Mary mix, lime juice and 2 teaspoons of the taco seasoning mix; set aside.
Moisten rims of four 16-oz glasses with one of the lime wedges. Place 2 teaspoons taco seasoning mix on small plate. Dip rims of glasses, one at a time, into taco seasoning mix to coat edge.
Fill each glass one-third full with ice cubes; pour Bloody Mary mixture over ice. Garnish each with lime wedge and cucumber spear.