Place the prickly pears in a blender and pulse until liquefied. Strain the juice into a small bowl (you should have about 1 cup of juice).
Fill a large cocktail shaker with ice, add the prickly pear juice, tequila, triple sec, lime juice, and sugar and shake vigorously.
Pour into glasses filled with ice, rimmed with salt or sugar, if you like.
Garnish with lime slices.
For a fancy party cocktail, combine some chipotle chile powder with your coarse-grained salt before rimming the glasses. The smoky, spicy salt will make a nice complement to the sweet, fruity drink.
