Gunny - no enduro motorcycle experience to speak of, but I did bicycle through South America with my brothers a few years ago. Feel free to PM me for tips on Patagonia. We rode south through Santiago, crossed east into Argentina from Temuco to do the 7 Lakes Route and eventually linked up with the Carreterra Austral. Rode all the way down to Fitz Roy, Torres del Paine, finished in Ushuaia. Patagonia is truly unreal, something to behold, you'll never forget it. I'd recommend just sticking close to the mountains and the Carreterra Austral and avoiding Argentina's Route 40 as much as possible. The ripio will be jarring and the harsh wind and endless expanse of scrub brush gets old pretty quick.
If you change your minds on motorcycles, keep in mind that bicycles are easily transported via airplane in a bicycle box. Eliminates the hassle of buying/selling/registering a motorcycle. If I had a month, I would take mountain bikes and fly into Puerto Montt. Beautiful time of year. Ride the Austral in Chile and 7 Lakes loop in Argentina, tent camp when possible and otherwise splurge every few nights on a hostel stay or do like we did and make friends with the old ranchers and enjoy sleeping in their barns and swapping stories over coffee. You'll never forget it and you can take your bicycles back for more adventures in the States and elsewhere. With ideal group size of 3 you can spread load the weight of tent / stove / tools and it's that much easier to get off the bikes for resupply and tourist activities.
Would love to see photos of the journey when the time comes! I love that part of the world.