Yes, you can rush as an upperclassman. I know that the sophomore and junior women going through sorority recruitment get bids there -- I'm not sure about the guys, but it wouldn't surprise me if it's the same. Go through rush and see what happens.
http://www.usfgreeklife.com/home
If you edit the title of your post to include USF, you might get responses from people who have a better knowledge of your school. Good luck!