Jenn,
You can go on collegeboard.com and see what the average acceptable SAT scores for the USMA are. That being said, the numbers are somewhat subjective. The long and short is simply, if in doubt, retake your SAT's and ACT's as often as possible. My son took the SAT's 4 times - each time bettering one aspect of his overall score. By doing so he submitted SAT scores in the mid to upper 600's in each category. Although his file is strong you then have to take into account the applicants vying for spots! In some states and districts, the competition is so strong, many applicants wind up on the NWL and do not receive a appointment. 5 years ago many of these candidates would have received appointment - no problem.
Another thing to consider is that West Point looks at the entire candidate when determining who they select. They call it the WCS (Whole Candidate Score). While academics are the biggest component of the selection process, they also look at your athletic abilities (varsity letters, captaincy, awards...), Leadership qualities (organizations you belong to and your leadership role in that organization) and your DoDMERB status (to make sure you are physically able to handle the rigors of USMA life - and beyond).
Do you best in your academics, athletics and EC's and things will work out the way they are supposed to! Good luck!