Using lime slices, moisten the rims of four margarita or cocktail glasses. SEt aside lime slices for garnish. Sprinkle coarse sugar on a plate; hold each glass upside down and dip rim into sugar. Set aside. Discard remaining sugar on plate.
In a blender, combine the remaining ingredients; cover and process until blended. Pour into prepared glasses. Garnish with reservedlime slices. Serve immediately.