I have a very short customer who is on a Surly LHT, The smallest is a 46 cm, again we encourage people to go as big as they can with the frame and then work with stems, handlebars, etc for dialing in the fit.
You can change the 26 to 24 easily and add a 34 or 36 on the cassette, just fine tune the chain. So if you added a 36 in the back and a 24 in the front you'd really have some low gears. If you are a small person don't shy away from the standard LHT. Disc Truckers are certainly nice too but IMO, Disc Brakes for lighter people traveling on paved roads aren't something one has to have. You'll have plenty of stopping power with the standard LHT, especially as it sounds like you aren't planning on carrying a ton of camping gear. Feel free to PM me or call if you need more detail.

Good luck, Surly is an awesome choice. We had Grant Petersen here a few years ago and he loves them as well, great bike for the price.