If you go to this page --
http://www.npcbruins.com/sororities -- you can click each sorority name, then click the link to their local webpage and check each chapter.
You can also find each GLO's facebook link.
Since UCLA is not Rec-driven, there may be NO deadline stated. I don't know of any house at UCLA that has a deadline. I think most houses will even take Recs during Recruitment. (Don't faint.) To be on the safe side, you might want to get them in by Labor Day. It's not a deal-breaker if you don't.