No. Some schools do appreciate it if you know the native language, if for no other reason than to be able to handle yourself more comfortably in the environment. In some cases, you may even be offered more money. However, if you've been trained in the Direct Method (the method utilized in BridgeTEFL programs), you should be able to teach English successfully in any country in the world, whether you know the language or not. Furthermore, many schools offer language classes and social activities to help familiarize their teachers with the local culture.