Question about Audio Books directory and Play All/Random

I like to listen to podcasts on my Sansa Express, but also like to randomly listen to all of my music.  I do not like to randomly listen to my music and then have a 1hr podcast tossed in the middle.  I was wondering if Audio Books are excluded from the Play All/Random settings so when listening to music it did not toss Audio Books into the mix.  I do not have any Audio Books so have been unable to check this out on my own, but would greatly appreciate it if anyone could let me know what happens.  And I would also appreciate knowing what directory the Express uses to store Audio Books so I can see what happens if I put a MP3 of a podcast in the same directory that is normally reserved for Audio Books.

Thanks,
Jim