UCLA usually has a junior quota (almost always 2). Some chapters may take more depending upon their class distribution.
Juniors usually do very well in COB, but that doesn't mean they shouldn't go through formal recruitment. Formal recruitment is a TERRIFIC way to see all of the chapters and get to know the women. I highly encourage you to check it out. You can register here:
Go Bruins!!!!
When I went through recruitment my best friend went through with me as a junior in credit hours. She wound up in a terrific chapter (we joined different groups), and we had some great juniors in my new member class.
Good luck!