From what we've been doing is we've been checking .po into source control because we have some translations alread in our .po files that we don't want to lose as we add more entries.

Django is very good at not deleting things from the .po file. If previously used messages are no longer used, django comments those messages out so as to not accidentally delete them.

Also to make messagefiles available to django you need to run `django-admin.py compilemessages`. See [this](https://docs.djangoproject.com/en/dev/topics/i18n/translation/#compiling-message-files).

To handle actually getting things translated you might want to check out [django-rosetta](https://github.com/mbi/django-rosetta) - it has a really nice interface for someone to be able to track/translate messages.