(I guess we're supposed to assume that Valjean wants to stay close to his buried financial resources... but I dunno, that's kind of thin, given how easily he acquires them when he needs to. The fact that neither of them speaks anything but French? I dunno. I'd have to agree with you that he's probably just not interested in it, and/or not interested in being an immigrant who doesn't speak the language, so that it doesn't much occur to him as an option.)