Prune off any Aztec grass blades that brown at their tips when the weather drops. This will prolong the Aztec's green beauty a little while longer as the growing season wanes.
Mow the Aztec grass down to the ground once the the majority of the grass blades die back at around 20 to 30 degrees. Set your mower to the highest blade setting available. Cutting the Aztec grass at ground level may kill it.
Stop watering the Aztec grass once its foliage dies and after you cut it back. It won't need to be watered again until spring. Resume your regular watering schedule once the weather warms in spring and the plant produces new growth.