In the past decade or so, the number of such programs has exploded, and most selective colleges now offer some sort of on-campus "diversity weekend."
Hispanic students do get a "hook" in the admissions process at Princeton. Institutions that were known for decades as bastions of white privilege are certainly looking to diversify their students bodies ...
This part of the application process can be confusing (along with the rest of it, of course :-) )
Transitioning to college life can be challenging, and living in a place with students who share your academic talents and focus may help to make that transition smoother. You will have plenty of opportunities to mingle with other classmates, regardless of where you live on campus.
Colleges most definitely DO evaluate you in the context of the high school you attend, and admission officials clearly understand that an "A" at some schools is nearly impossible to earn, while--at others--you can score an A+ just by handing in all your homework!
If your daughter is applying to colleges that require the SAT II Subject Tests (and many of the more selective schools do, although not all) then she still MUST take them, even if she is doing college-level work right now.
Being in a magnet school will NOT hurt your admission chances at NYU or at other highly selective schools, even if no AP classes are offered. Admission officials will evaluate your transcript in the context of WHAT IS AVAILABLE TO YOU.