Go for it. Don't let the fake/catty attitude of other PNM's get to you - concentrate on the sisters. Sometimes PNM's will backstab other PNM's, thinking it will increase their chances of getting a bid by ruining someone else's chance
but such women are often cut early on.
When you get to later rounds, especially pref, take a look at the other PNM's who have been invited... anyone invited to pref is a potential sister, so sororities choose very carefully whom they invite, and these women are potentially your pledge sisters. If you see a lot of PNM's obviously being fake, catty, rude, etc. - it might not be the sorority for you.