Re: How many instructors teach Ukemi Waza?
If the style you practice does a lot techniques in such a way that breakfall ukemi is required in basic waza, then like Judo, not a bad idea to start breakfalls from day one. If your style emphasizes doing basic techniques so rolling ukemi is most appropriate then it's good to really work on rolls, all kinds, learn to control and direct. Actually at least in Ki Society, it's seen as a continuum where there is no difference between our rolls and breakfalls. Just a shift in timing and rotation in response to nage's actions. So rolling practice is seen as an intro to our method of breakfalling. That said, I do tend to introduce some breakfall exercises in warmups and basic classes that students can do before they are actually taught to breakfall after learning good rolling mechanics. But frankly, they simply don't need to learn to breakfall right away since the only techniques where we do technique with breakfall being the only option are when weapons are involved.
of course ukemi is not just about how to fall.