I have the denim version of this skirt:
http://shop.nordstrom.com/s/ha.....rt/3295803
The reviews on this one *and* on the cotton version say they run small, compared to the popular Halogen seamed pencil skirt. I usually wear a size 8-10 in most things, and a lot of my skirts are a size 8. I trusted the reviews re: sizing on these, and ordered a size 10. It fit perfectly. Keep in mind though, I'm battling some extra pounds that weren't there last year. I'm up about 5-7 pounds these days, so it might be that this particular skirt is actually true to size, whereas perhaps the seamed pencil skirt runs large.
I know it's a hassle, but if I were in your shoes - I'd order my regular size and maybe one size up, and just return the one that doesn't fit. I haven't yet returned things to Nordstrom via parcel, but I think they include a label and so on, making it relatively 'easy' to return if you don't have a store nearby. In addition, based on something I heard from Marianna (I think), I asked at my local Nordstrom Rack if I could return Nordstrom orders there, and they said it would be fine to return there. The Rack store is a five minute drive from me, whereas the regular Nordstrom store is half an hour away.
If you have to ship something back - most UPS stores are open on Saturdays, and since they send you a return label, it's just a matter of dropping the parcel off.
I'm betting that these skirts (the stretch denim pencil skirt and the stretch cotton blend as you mentioned) are more 'true to size' than running small. Just that if you need a skirt for your upcoming travel, you might consider ordering two sizes to make sure that you get one that fits in time.