Why would you want to cut them back in the fall when they're at their best? Wait until spring.

You can cut them back in late fall if you like. You're in a warm enough zone to do that. Just be aware they will be more exposed to very cold weather, and be ready to protect them in the event of a very cold snap with no snow cover. The winter foliage traps all sorts of leaves and other detritus and provides protection to the crown of the grass. If you take it down, you'll have to be prepared to give that protection if it becomes necessary.

In zones colder than 6, I wouldn't recommend it.