Does the pattern tell you what kind of yarn to use (worsted, bulky, super bulky)? I would think with such large needles that you would be wanting bulky or super bulky.
If no yarn size is listed, you may need to buy a skein of both bulky and super bulky yarns and then do a test swatch to see how many stitches per 4 inches you get. From that, you'll have your gauge, and then you can start looking for the perfect yarn.
Also, you might check on Ravelry.com (free to join) and see if anyone there has made this pattern and what kinds of yarn they used. You can search for it by name, and then look at the "Projects" tab to see if other people have it in their project lists.