Hello searchingforhlp. The short answer to your question is YES! To my understanding (and I'm sure someone will correct me if wrong) you are NOT prohibited from joining a NPHC organization if you were NEVER a part of one before. True, as my soror stated above, some might question your loyality; but that within itself doesn't restrict you from applying for membership.
I say go for it ONLY if you are willing to make a life committment to that organization because once in that's it-- no turning around. Yes you can always disassociate yourself, but you can NEVER seek membership in a NPHC org again. So I STRONGLY advise you to DO YOUR RESEARCH and look at the organization as a whole (nationally) as well as your local chapter because this is a life long committment. You don't wanna look back one day with "woulda shouldas" because you've grown disenchanted with the sorority because it wasn't all you hoped. Only YOU know what's important to you in membership.
That's just my opinion for what it's worth. Hope that helps! Good luck.
