you don't have an acceptance yet, so you wouldn't be declining an acceptance to begin with...
but anywho, are you ONLY applying to 3 schools? sounds to me like you need to add more schools unless you're really determined to stay near home for some reason.
but anywho, only apply to schools you'd attend. there is no point in applying to a, b and c when you'd only go to c. reapplying after an acceptance to a and b would look foolish on your part. i've seen a few threads on that.