Combine mangoes and juice, tequila, limeade, Triple Sec or Cointreau, and Grand Marnier in a blender. Mix well. Pour half of the liquid in a pitcher and set aside. Dip margarita glass edge in reserved mango juice and then sugar. Add crushed ice to liquid in blender. Blend until margaritas are slushy.

Note: As an alternative to using mango juice, sliced limes can be used to wet the rim of the glasses.