I went through a similar situation just this last fall. I was a junior who went through rush this past fall and I can tell you...it was hardly the let down I expected. In fact, it was better than I could have ever hoped for. While the greek system at the University of Wisconsin is not as large as your school, that can only work for you rather than against you. Staying postive about the whole experince helps alot. I heard the same thing that it will be diffcult for juniors to get into the "top" houses, but I was invited back to all of the "top" houses (both my first choices and the typically popular ones) for every round and some all the way to pref. But beyond the high hopes, you must also be realistic...Let's face it, there are just some houses who will not bid Upperclass men no matter how well you got along. I had an awesome rush at a house that cut me immediately after first rounds and was invited back to a house where I thought I completely had made an ass of myself.
When going through the rushing process focus on your postive qualities of being an older rushee,espically when discussing your status with your rusher:
+ You have an established gpa & are adjusted to the work load of college.
+ You are are much more serious about joining than a freshman who merely thinks its the thing to do.
+ You are prepared to be involved right away since your time is limited.
+ You are confident enough to go through rush beyond a freshman. Its like dating, you want to show interest, but don't act too intrested like it will crush your world if you don't get a bid.
+ It also helps to have a sob story or a some sort of "personal reason" to share...I'm not advocating making one up...but I used my recent break up of a 2 year relationship prompted me to go out and meet new friends who didn't know me as so and so's girlfriend -AND- My family was all greek and alot of my old friends are at other schools and they seemed like they had a good time. Opening up to the rusher really helps them relate to you and chances are they will sympathize with you which only helps your case.
+ If you don't plan on graduating in four years, MENTION IT! Say something like..."Well Im a junior, but with the way things are going credit wise- I'm more of a sophmore."
Well, thats basically all that I did. And I had a great time. Above all don't see rush as a do or die job interview...the more you think of it as playing karmic musical chairs, you will be fine...you will find the right house for you if you just let it happen.
Good luck and best wishes!