Using lime wedges, moisten the rims of four margarita or cocktail glasses. Set aside limes 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 lemonade concentrate and raspberries; cover and process until blended. Press mixture through a fine sieve; discard seeds. Return raspberry mixture to blender; add the ice, strawberries, blueberries, sugar and tequila if desired. Cover and process until smooth. Pour into prepared glasses. Garnish with reserved limes. Yield: 4 servings.