I agree with Moee: for me personally I don't think deja vu would be a very good dream sign, if only because it almost never happens. On the other hand, if deja vu did happen, I would definitely RC, as that is something that could easily occur in a dream, and might be an excellent indicator that you are dreaming. I think it would be sort of foolish to have deja vu, and purposely not RC simply because "it's only deja vu."