If your skorts are riding up it's because they're either too small overall, or, specifically, too short in the rise (a common fit issue for long-waisted women). Rise is the distance from crotch to waist. You can buy jeans in short, average or long-rise (Wrangler Auras, for instance), but I've never seen ready-to-wear skorts with those options. The other option is to go up a size. This will allow you to wear them a little lower on the hip so you don't end up chewing cloth.
Kathleen