I know that you can delete the watch faces; I haven't come across away to sort them. I do think though that the faces appear in the order in which they were created, so if you delete the faces you don't want/use often and then remake them at some point, the two remaining that you use often would be next to each other.
Yeah, that's what I figured...just not ideal or something that you would expect from Apple...there should be a simple way to arrange them, even if using the app on iPhone. Hopefully this little feature is added in the next update (after they fix all of the other issues of course!).