Ah. Found it. In Expert mode with the Timeline visible, one right clicks on the timeline and in the long list of right click options there's Delete Audio.
Now to go find out what other helpful options are in that right click :-)
Interesting. Do you cover things like hints and tips on actual creation of 'ok to watch' videos ..... for example to help with ideas that might make a video watchable :-)
What's unwatchable about your videos? Is it the technical quality of the videos themselves or the content?
If the latter, you may want to check out my article on telling stories with video at Premiere Elements support site Muvipix.com.
Along with Steve's excellent books, here are some additional resources for learning PrE: http://forums.adobe.com/thread/800455?tstart=0
You will see Steve's name mentioned in several of those, like is Basic Training Series and Learning Series. There are also some AdobeTV tutorials, that I find very useful.
Good luck, and happy editing,