Even if he did understand you, he would pretend that he wouldn't. [That's Norrington's opinion of Frenchmen.

He holds out a bent arm for the girl to take.]

Allow me to escort you to your destination, miss. Tortuga is no place for an unaccompanied woman of virtue. [Although her clothes don't look virtuous at all, but Norrington has travelled sufficiently far and wide to know that people from foreign lands have very different ideas about appropriate dress.]