Eileen, you might want to think about some of the floaters that will be added. They can all be pieced, but there is one wide one (with the dots) added in month 12 that requires a total length of 72". You might want to think about what fabric you will use there. Sue's fabrics are basically solids. I didn't do the dots and actually used a floral print that I had enough length so that I didn't have to piece it.
As for how many fat quarters, you will use a total of about 17-1/2 yards of fabric in addition to the background so that would be about 70 fat quarters. It may take more, depending on how matchy-matchy you want your finished quilt to be, because cutting out of fat quarters produces some waste. For my scrappy version I started with about 100 different fabrics, but some were smaller pieces and some were larger. They were all pulled from my stash.