Here is what Stanford states about AP scores:
Students currently enrolled in AP courses are not required to submit AP scores as part of our admission process. AP scores that are reported are acknowledged but rarely play a significant role in the evaluation of an application. Grades earned over the course of a term, or a year, and evaluations from instructors who can comment on classroom engagement provide us with the most detailed insight into a student’s readiness for the academic rigors of Stanford.
http://admission.stanford.edu/basics/selection/prepare.html