I am also a Zumba enthusiest!! I've been doing it on and off for the past year. And it is a BLAST!!!!
To wildgrits - There is a special class for 50+ aged people that is called "Silver" or something like that. I've found, thought, that if you just go to a class - stay in the back - and modify as needed...you can turn any Zumba class into a lower intensity class. When I have been away for awhile, I'm in the back going slower. But after a few weeks...I like to be near the front :-)
To ZumbaChica23 - I have a good friend who went through instructor training a few months ago. She now teaches several classes each week! And she is still on her weight-loss journey! Why wait...start now!