Which foods should be avoided by people with huntington's disease?

Choking hazards. No specific food needs to be avoided. It is the size and consistency of the food that matters. In early stages of huntington's you need to be sure that food servings won't cause choking like large pieces of hot dog or meat. In late stages of huntington's, foods that are too liquid may cause aspiration, so thickeners may be needed.
Eat what you wish. Nothing will slow or speed the brain pathology. Huntington's patients often have swallowing difficulties; a high-protein, high-calorie (your energy needs are high), soft diet often works best. If swallowing liquids is difficult, thickening agents can be added. Huntington's is very difficult and I am glad you are taking a pro-active approach.