I lived out there for 10 years and used to do a lot of day trips around the front range but no multi-day excursions. I would definitely shoot for July or August. Winter can run long and if it was a big snow year the higher elevations can still be covered into the summer months.
Do you plan on camping?
It is beautiful out there no doubt, just a shame were it has gone politically (and why we left 2 years ago). I do miss the trails, hiking, atv's etc. though.
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Probably not camping, i'm too high maintenance now.