From what I understand, you want the users first name and last name to be automatically translated from French to English (does that even make sense?), which is not possible right now, as it requires strong AI.
If you just want the messages "First Name" / "Last Name" to appear either in French or English, have you read the introduction on languages and resources howto?
Keep in mind that your program does not need to change the keyboard - that is the users preference (and I would be quite annoyed if a program would take such initiatives...).