Attire for a job fair??

I think your thoughts are on track. "Business casual" is a nice comfortable compromise. The employers at the fair will not expect you to wear a suit -- but the blue jeans, crop top, sandals, etc. look doesn't give a professional impression. Choosing something in between -- such as nice slacks or a skirt -- is a good choice.

A few more tips:
1. Bring copies of your resume if you have it. It will help them contact you later and gives you a chance to "show off" a little.
2. At least pause and ask a few basic questions at instititions in your geographic area even if you doubt you want to work there. It will help you to know what the "community standard" is for things like orientation programs, scheduling, compensation -- so that you can view the hospitals in which you are most interested into proper perspective. Comparing institutions in different geographic areas is a bit like comparing apples to oranges.
3. Don't forget to smile.

Good luck!
llg

Clean neat dress pants, tailored top or plain sweater, low heeled shoes, minimal makeup and jewelry. Hair neat and clean. Nails neat, no purple polish. If pants are not the thing, then a simple tailored skirt, or dress.