I live in Austin, Texas and I have had my girls about 18 months. Black Stars, Buff Orphingtons, Golden Sex Links and americaunas were in my first set of gals and they have all done very well. I installed a misting system on a timer to my sprinkler that goes off in the late afternoons when it is over 100. That brought things down enough that I never had issues with lost production or dying girls. I have a nipple watering system which is hooked up to a rain barrel. I catch water when I can but I also refill the barrel as needed so they are never out of water. I personally adore my Buff O, but it is due to her incredible personality and love of people. She is a spunky gal! My second favorite breed are the black stars...they produce well and are very personable.
I have gotten new girls since including a buff brahma and a partridge rock. They are only 6 months old and aren't laying yet so it is too soon to say if they will do well in the heat, but the place I buy them locally sells a fair amount of them so they should be fine.