Disclaimer: I'm a native English speaker, so grain of salt.
It depends a lot on the kind of game. Some games are pretty easy to play only on visuals and small bits of text. For something text heavy, like an adventure game usually might be, I'd think most people would not try it unless it's in a language they understand well or want to learn.
For an individual game, I'm not usually that upset if it's not in my language - Lotta games out there, I can just move on. But if you're making an engine and hope to keep using it and maybe expand the scope of your games - I'd say start trying to implement i18n support sooner than later. Even if you don't have time/resources to translate the games yet, it'd be good to make the code ready for it.
