Oh, yes! This is exactly what I wish too. I hate playing with normal subtitles, but I've noticed time and time again that when NPCs speak other languages the subtitles only appear if I have all subtitles enabled. I often have to quickly press ESC and then enable subtitles in order to understand, but I invariably miss out on the first line or two of dialogue.
If anyone is listening, please think about adding an option of language sensitive subtitles as sf0912 suggested above. This would be fantastic.