OK, as to language I'm going by http://nanoha.wikia.com/wiki/Device]the device page on the Nanoha wikia. The general gist of things is that the Device speaks the base language of its Magical System (English for Mid-Childan, German for Belkan), but due to the synchronisation between Mage and Device the Mage always understands the Device.
The implication is the Translation Convention is in effect, and Devices can translate for their users (or that there are low-level and/or easy to maintain translation spells available. Telepathy IS a widely used spell/skill).
None of this PROVES that the TSAB doesn't use a Japanese analogue as their main language, but I'd be sceptical. Japanese as a majorly recognised language (among the OTHER Earth/N.A.W. 97 languages) probably doesn't become part of the standard language package until AFTER the Aces make their mark.
The implication is the Translation Convention is in effect, and Devices can translate for their users (or that there are low-level and/or easy to maintain translation spells available. Telepathy IS a widely used spell/skill).
None of this PROVES that the TSAB doesn't use a Japanese analogue as their main language, but I'd be sceptical. Japanese as a majorly recognised language (among the OTHER Earth/N.A.W. 97 languages) probably doesn't become part of the standard language package until AFTER the Aces make their mark.