My (admittedly limited) experience is what Silver said - ankle carry sounds like a good idea in theory but is hard to do in practice.
When my county finally gets its head out of its you-know-where about CCW permits - and I choose to believe it's a matter of "when" rather than "if" - I'll be looking at IWB carry when my daily wardrobe supports it and purse carry otherwise. I don't have even one garment in my wardrobe that would provide both effective concealment of an ankle holster and draw time short enough to matter in a self defense situation. In both of my prior tangles with predators, any holster that took more than a couple of seconds to draw from would have been too slow to help me.
Tammy (in Santa Barbara County)
"Courage is the price that life exacts for granting peace." ~ Amelia Earhart
"Experience is what allows you to recognize a mistake the second time you make it." ~ Unknown