Chosen answer:No. There are small instances on "Star Trek: TNG" where Picard speaks French on board the Enterprise, without the Universal Translator altering it. Were he always speaking French, the Universal Translator would make no distinction when he was speaking French as a matter of course, or speaking French for a particular effect. In the episode "Code of Honor", Data refers to French as an "archaic language" on Earth, to which Picard takes umbrage. I suspect Data would have known if Picard were actually speaking French at the time.
Chosen answer: No. There are small instances on "Star Trek: TNG" where Picard speaks French on board the Enterprise, without the Universal Translator altering it. Were he always speaking French, the Universal Translator would make no distinction when he was speaking French as a matter of course, or speaking French for a particular effect. In the episode "Code of Honor", Data refers to French as an "archaic language" on Earth, to which Picard takes umbrage. I suspect Data would have known if Picard were actually speaking French at the time.
Michael Albert