Steve:
I am from Louisiana a state in the southern part of the US that has simular climate you discribed. The USDA experimented with Brahman influnced cattle and developed a good cross that developed into the second registered american breed in the US and its name is Brangus. Brangus are 3/8 Brahman and 5/8 Angus. If you just like Simies you might consider using the same percentage and create a Simbrah (another american breed). these cattle are heat and insect resistent which is needed in your area. Contact the breed assocations of each breed for information for your area. Good luck,