It took me 2-3 classes before I got the hang of it, but after that my instructor would repeat the same routines and the moves got easier. In a public class everyone is in the same boat, and there is usually a wide range of people of different ages and fitness levels. I went alone and never felt intimidated or out of place.
Zumba is a good cardio workout and fun, but overall I wouldnt rely on Zumba to get me to my ultimate weight loss goal or to help take my fitness to the next level. I go once a week, and it's part of my workout schedule....but circut training, body resistance moves, and weights are what's helping to reshape my body. Zumba is kind of more stress relief and lighthearted compared to my other workouts, and I absolutely love my Zumba instructor...the energy in her class is very motivating.
So I say Yay and that there is no harm in trying it out, but give it a few times before you decide whether you enjoy it and if it's value added to your workout schedule.