Before you forget all that high school French, you might want to take the Yale language placement test now and save yourself a lot of time later.
All students at Yale have a foreign language requirement. You are exempt if you got a 4 or a 5 on a language AP test, but otherwise you must take two years worth of foreign language classes — unless you place out of some of this study through a placement test. These tests occur almost immediately after you arrive on campus.
As for other AP credits, they can be used in a complicated and somewhat arcane system of “acceleration credits” at Yale. Ask a freshman counselor or read the Blue Book for the exact rules, but one thing to keep in mind is that acceleration credits are only applicable if you plan to graduate in fewer than eight semesters.