I went to Zumba for the first time today and my instructor was a girl I went to school with, and she spoke the whole way through.
On most of the dances she went through the basic moves before playing the song.
Whether that was for the benefit of the newbies, or if that's just what she does, I'm yet to discover.
However, during the dancing, she told us the next move coming up, encouraging the class etc.
Come to think of it, she had a microphone headset on. Surely if she wasn't to speak during the dancing, she wouldn't need to wear one as she wouldn't have to compete with the music.
I think her in instruction really helped, as I got lost a few times, and I don't think I would have enjoyed it half as much as I'd've just messed up all the dances, felt a failure and not wanted to go back.