Having sort of been in your situation (I'm an east coaster who went to Bolivia for a month on very short notice), I would say agree with edoc that physical conditioning is pretty much all you can do out East in terms of preparation. I would just emphasize that when it comes time for the actual trip, the importance of acclimatization cannot be overstated. For me, this was by far the biggest issue, and unfortunately one that you cannot prepare for by training back home. That said, you can begin your altitude preparation here, in a sense, by planning the trip carefully in such a way as to minimize the effects. Start by getting a Diamox prescription from your PCP. Don't wait until you feel like crap to take the diamox - start taking it while on the plane. Plan your trip with as much acclimatization as possible - 4-5 days MINIMUM, a week even better, if time allows. I know you're from Colorado and know something about altitude, but the Andes are a totally different story. Anyway, acclimatization strategies is not the topic here so I won't go into any further; my point is that in my experience, this is the single most difficult issue about high-altitude mountaineering, and your best preparation is a combination of maximum physical conditioning and an itinerary that emphasizes acclimatization as much as possible.
P.S. I have not been to Artensoraju but know people who have, and from everything I hear it should be amazing!