It's two hours north (from Richardson, Texas). Going off season means you won't be swimming in the falls, but the admission is significantly less expensive.
And you could throw in a visit to the fledgling Toy and Action Figure Museum (for the kids of course), $6. It's 35 minutes more north. It was through a community visioning exercise that the Museum came to be and it is an example of a small community trying to bring in tourist dollars. Around the same area (Pauls Valley, OK) are the little Amtrak station (Heartland Flyer runs OKC to FT Worth) and Bedre Chocolate Factory (Chickasaw Nation).
