I was in Joanne's this past weekend and they actually have several Fall plaids on display. Don't know how many are "tartan's", but there are several very nice plaids.

In my experience, this fabric will work for kilt making, it does hold pleats nicely and is medium weight. I make them with a Sportkilt like pattern which is basically a wrap skirt with pleats fastened with velcro. They look good, they are good summer / fall wear and the general public doesn't really know the difference (even if they cared). If it's plaid and knee length, the assumption is "kilt".

I plan on purchasing a couple of different fabrics and making a couple more kilts. For some odd reason, I can never have enough kilts -- don't know what that is.