Hi, I'm a USF alum! I will first tell you Congratulations on deciding to go to the school that DOMINATES the one sided "War on I-4" (
to all my UCF peeps on here!)
Anyways, I would invite you to visit USF's Panhellenic website.
http://www.usfpanhellenic.com/ It has been re-designed and updated. It has profiles of all the sororities, information about recruitment, and contact info for Panhellenic Council Exec Board members. Feel free to call the office, there are plenty of them working in the Greek Life Office all summer.
As far as your questions go, since you are a Junior, you should definitely let all of the sororities know that you will be in school for a couple more years. It is "U Stay Forever" so girls should take it into consideration. There are no guarantees however, some chapters will not take juniors and seniors.
Most sororities have meetings on Sunday nights, with the exception of Tri Delta, who usually had their meetings on Monday nights. My sorority would have some Monday night meetings due to holidays, in those cases, the meetings would be at 9PM, which allows everyone with night classes to attend. (Night classes should end by 8:50)
As far as what to wear to recruitment, there is a style guide on the Panhellenic Website, and they will probably give you a brochure on Info Night with pictures of the Pi Chis (recruitment counselors) in appropriate clothes for each day of rush. You will be spending all day, every day outside, under tents, in Greek Park. My advice is to dress cool, bring plenty of water, and an umbrella!
Most importantly, have fun and enjoy the experience! I was a Pi Chi and on Pan Exec, so I loved recruitment from the Panhellenic side of it. Good Luck, and GO BULLS!