If you're an alto/mezzo, don't audition for Sarah ... she has several high A-flats and, I think, a high A or two. If you can dance and belt, Adelaide might be the best way to go. If you're a convincing belter, check out Adelaide's stuff ... "Bushel and a Peck," "Adelaide's Lament," "Take Back Your Mink," etc.
However ... if girls are being cast as guys, you might want to consider Nicely-Nicely. For a guy, it's a reasonably high tenor role, which might lie within your range if you're an alto. "Sit Down, You're Rockin' the Boat" is an absolute showstopper.
I'm in Guys and Dolls right now, so if you have questions, feel free to PM me.