I found this text guide to be very useful:
http://www.gamesradar.com/batman-arkham-city-harley-balloon-...Personally, I prefer screenshots and maps that I can follow along with as opposed videos. This guide shows the balloons in the order you can earliest access them while playing through the story.
Please be aware that this content does not allow you to free roam the areas after completion, so if you miss a balloon you may have to replay the story content again in order to get access to this area again.