Huh, huh, huh. You said matriculated.
Sorry, couldn't resist.
You could probably go through rush, but you could not begin pledging if you don't meet the requirements. Before we allowed 1st sem freshmen to pledge, many of them went through rush in the fall as a "trial run" but then again we didn't have a big ol rush fee either. If this is common at your school, it wouldn't hurt. I agree with Maggie, call the GL office and ask.