When I give a talk or class in Israel, I can be sure that people will interrupt me, ask questions, challenge my assertions, and generally push me to explain what I'm saying. These interactions make things more interesting for me, always teach me something new, and (I believe) also make the conversation more relevant for other participants.
By contrast, my experience with American audiences is that they're much quieter and reluctant to challenge me during the talk. They'll wait until the formal question time at the end, and then raise issues.
And during the two classes that I gave in Beijing, participants were even quieter than Americans -- although the second group I taught (this year) were far more vocal than the ones I spoke last year, so it might have as much to do with corporate culture and their English level as anything else.
Bottom line, try to get a sense of the audience, and how they expect to interact with you. Then you can prepare an appropriate balance of prepared notes vs. discussion with the participants.
Over time, you'll get better at making these judgments and estimates; like everything else, public speaking is a skill that takes years to improve. But it's a real rush to give a good talk, and to know that you've taught others something that they didn't previously know. So do your best, and know that next time, you'll hopefully do even better!
I believe this is a crapshoot. Many times audience participation is more accurately described as "audience interruption and diversion". If you let them, a single audience member can easily derail a presentation in ways that all of the other audience members are not interested in.