Yarn Substitution Game

http://www.yarn.com/yarns/zephyr.html

I'm trying to find my perfect yarn. Could someone please tell me if this yarn would be suitable for the Garden Shawl? I don't know what 18-20 epi means and can't seem to find a weaving dictionary. I think this might be ok, but I would like some "more expert than me" opinions. If you care, I'm thinking about either the Plum or the Sable color. This would be way more yarn than I need for this project, but I don't care about that right now.

Thanks for the help,
Katy