I was in Branson this past weekend for my Sister's wedding and was very surprised to find an excellent mexican restaurant in the center of a culinary wasteland.
Casa Fuentes is on Highway 76 about a mile toward the heart of that godforsaken place from Highway 65. It's a little two room, maybe fifteen tables, restaurant owened and operated by the Fuentes family. The menu ranges from your standard tex-mex fare to more authentic moles, sopes, even menudo!
If you have to go to Branson you should just plan on as many meals here as possible. It's relatively cheap, is open for at least lunch and dinner, and DOES NOT have a "buses welcome" sign.