Is it a 'bug', as in the software working in a way you didn't expect?
Yes, feel free to post it here. On the international sites, it's not just the content that is in another language, it's also the entire UI. Translation tools like Google Translate do help, but it also breaks things, which might result in certain buttons not working. Still, we want these reports, and want people very familiar with how our software is supposed to work letting us know if they find something odd.
Please try whatever you were doing without automatic browser translation prior to reporting. The translation process itself can break things in odd ways.
Just keep in mind that these reports are very specific to certain sites, and might not stay around for long after being fixed.
Add the internationalization tag to your report, we'll see it.
Is it a translation issue?
If you've spotted a missing or incorrect translation it's probably best to simply report it on the appropriate per-site meta, if you're comfortable enough to navigate around enough to post. Remember, automatic in-browser translation can subtly break things, so we recommend turning that off if you intend to actually post something on the site.
If that's simply not working for you, you're welcome to post it here. If you found multiple translation issues, please just consolidate them into a single report. It's also very helpful to take a screen shot of the problematic text so we can immediately see it in context, and this usually obviates the need to translate the report itself.
Is MSE really the best place for this?
99% of all bugs get reported directly to the per-site meta sites. However, we currently lack a proper bug reporting mechanism within the translation interface itself (working on that), and we want people that find bugs or potentially embarrassing translation issues to be able to let us know - even if they can't navigate around an interface that isn't at all in English.
Meta, for now, while not ideal is the best place for these exceptional cases to land in order for the International team to sort them and get them off to a more appropriate place.