Well, I never took Zumba (does look like fun!) but I'm south american and have gone back fully to latin dancing at clubs, parties, while cooking, on the subway stop, (not in the shower at the gym, guys just would not understand).
It's a cultural thing with me, and typically when you dance you want to go all out (otherwise latin people will discreetly ask you to sit, since you're embarrassing the culture). So far it's been countless parties, three weddings, four graduations, one christening and one quinceanera.
My niece was up for a Boston Music award as the best DJ in Boston (placed, but no win), so I have had to support her in her endeavors at the clubs she works.
So both hips have gotten quite the workout in almost four years. Cumbia, Salsa, Merengue, you name it, it's been done. So I can report that the hips are MUCH improved for dance at high RPMs.
I started slowly, but was dancing comfortably at speed at about a year.