In addition to the routes cyccommute mentions, I might also be tempted to play it by ear and if it turns out you have a day with strong tailwinds from the south, I might turn north even a little earlier at Lamar, Rocky Ford or even Granada. The US highways in that part of CO don't have huge shoulders but traffic is often lighter (US 287 is probably heavier than average though not necessarily worse than US 50).

I wouldn't necessarily turn north earlier if it weren't for wind, but if I were facing a choice between slogginga day against a 20-25mph wind from the SW and heading north for a bit, I would reserve the option to go north first. I've done the same thing though opposite direction when I went from Fort Collins eastwards to Wichita, pick my days to take advantage of the winds.