When my commute was shorter (1.5 miles!), I biked in skirts all the time. I sometimes did this on my diamond frame, sometimes on my mixte. Wind was often an issue if my skirt was knee length & flowy (like most of my skirts), so I got smart and learned to carry a clothespin with me. I would pin the front of my skirt around my top tube or to my downtube water bottle cage (on the mixte) so that it couldn't fly up. Worked like a charm!

I have never biked in a real (non biking skort) miniskirt, but I'm also too old to be wearing them anyway.