If you have general questions (i.e. What's a competitive DAT score at X school, what's a competitive GPA, etc.), there's no harm in asking an adcom (although most of that information is probably already on their website.) Asking adcoms at schools you're applying to this cycle to review your PS prior to applying seems like it's introducing a conflict of interest. If said adcom who helped put together your application is later reviewing your application, it doesn't seem like they'd be completely objective. I think asking your school counselor to review your materials is probably more appropriate.