I'm so happy you have more than one house to go to!!! you should definatly go back everywhere you have an invite, if nothing else it could help accentuate the differences that make your top choice feel like home. or you could meet some new girls or have some new experiences that would make you open to accepting bids at more than one sisterhood. I'm also interested in your formal experiences (since i am no stranger to bad formal expereinces, I had 2!!!) If you're comfortable with it, that is.
Either way, have a great time... Saturday's only a day away!!!