Lately I've been attending classes for Tibetan Heart Yoga, which focuses on quick-moving series that can be really physically demanding. This class usually has about half males, while the basic yoga class I was taking before was mostly females. So I agree with babuji that the more "difficult" classes tend to have more males.
If you still don't know what a sun salutation is, I would say keep going to the more basic classes before advancing to the more difficult. Although, yoga poses are easy to modify to make them either more or less difficult, but it's crucial to have a good teacher who will let you know what the modifications are and when to use them!