Place 2 teaspoons sugar in a saucer. Rub the rims of 6 glasses with 1 lime wedge; spin rim of each glass in sugar to coat. Set prepared glasses aside.
Combine watermelon and next 4 ingredients (through Triple Sec) in a blender; process until smooth. Fill each prepared glass with 1/2 cup crushed ice. Add 1/2 cup margarita to each glass. Garnish with lime wedges or melon balls, if desired.
Note: If your blender still leaves it a little chunky you can mix the watermelon and sugar first, then strain puree and then add in the rest of the ingredients. Much better and less chunky.