If only using TTS:
Go to Settings>Skin Settings>Warnings>Road Signs..scroll down to "Choose Sound and Voice Road Signs" (It may say "no sound|{language word}").
Tap that category and choose "Reset" at the bottom..you may have to do this more than once until {language word} is gone and only "no sound" remains.
Repeat for "Turn restriction" and other categories that announce a word you do not recognize (might as well check them all).