Here is the dress I wore last week. Wearing skirts and dresses isn't really difficult when on the bicycle, unless of course you are already uncomfortable wearing them off your bike, right.
Wear what you want. If you are comfortable wearing any of your clothing or shoes walking, you'd be comfortable on your bicycle. That is my theory :D
I received an email the other day about skirt guards and I have not really thought about them because I don't think that the length of any of my dresses or skirts I wear, gets in the way or near the rear wheel – however, something I would highly consider before a skirt guard would be a chain guard. I think my tights would appreciate not having greasy-cool bike ring marks, though I think I'm pretty good about staying stain free. Coffee stains, now that is just another story.