I think your sorority "friends" have already been totally honest with you without trying to hurt your feelings. As other have mentioned, the chapters doing spring recruitment/COR are most likely the only ones who would be most open to a junior anyway. Waiting for fall formal may even decrease your chances as you are competing with many other women, mostly freshmen. A pnm in your position doesn't really have the luxury of "looking at all the chapters" because frankly, most of the chapters are not going to be looking at you.