Purists may disdain frozen margaritas, but purists don't have the upper hand in San Antonio. This version keeps it simple, with fresh lime juice, tequila, sugar, and lots of ice blended into a frosty mass and served in a salt-rimmed glass.
Puree ice, tequila, lime juice, and simple syrup in a blender until smooth. Pour salt onto a saucer, and moisten the rims of 4 glasses with lime wedge. Dip each glass into salt, and fill with margaritas. Serve with lime wedges.