There are several options available around Dallas including me. The Federation of Fly Fishers website lists the contact information for the area's IFFF certified instructors.
If you're looking for someone in Dallas, Travis Moore at Tailwater's is good. If you're willing to travel a little bit, Steve Hollensed is about an hour north of Dallas and he is one of the best in the country.
FFF Certified Casting Instructor
TFO Pro Staff