Well if thing is in a language I don't speak at all (like animes) I prefer to have subtitles (in french or english doesn't matter I'm good with both).
For english shows, I can deal without subtitles depending how crappy they speak, sometime without subtitles I would understand nothing but I'll usually put english subtitles, I don't really see the utility to put french subtitles because it won't help to understand more what they say in english.
In french, which is my first language, no subtitles please, ok in some case surronding souds loud and you can barely hear what the person saying but it is rare.