If using salt, pour onto small plate; mix with pinch of cayenne pepper so salt is speckled with red. Moisten rims of margarita glasses with a damp towel; dip glasses in salt mixture, tapping off excess.
In bowl of blender, add ice cubes, tequila, mango pulp, lemon juice, orange liqueur and sugar. Blend until mixture is combined and ice is crushed, about 1 minute.
Pour frozen margaritas into glasses; serve immediately.