I tried for two hours to get the audio to preview in the Sequencer. I finally got it to work by hitting Alt + A or going to the middle video sequence editor window > view > play back animation in all sequence areas. This kind of thing should have an icon, instead of going menu hunting or randomly hitting shortcuts.
You can also do that from the play button on the timeline. You just need to make sure that the sound is turned on by pressing the speaker icon to the right.
I thought that was for video/audio sync.