I usually do this check before using the ITranslationManager adapter:
if ITranslatable.providedBy(context):
tm_context = ITranslationManager(context)
The ITranslatable interface should be added automatically when you add a multilingual behavior to this content type. I assume this is done for the standard content types, when installing p.a.m. Maybe you can check, if there is any of those behaviors?
huh? I used plone.app.multilingual for translating a standard Page...so I would expect that everything else happens upon installation..sorry, can't this right now...