Kelly,
I've spent many summers in and around Estes Park, both as a kid and as a Park Ranger. During that entire time there were no strips, public or private, in the immediate area. However, there are places on Devils Gulch and Dry Gulch roads which I've eyeballed as potential landing sites - landing on the road where the fences are low and far from the road surface. Personally, I wouldn't try this without making a face to face visit with the locals.
What looks like gently rolling meadows probably won't be. I've traversed many meadows in those areas and found them to be full of badger holes, hidden boulders, swales, etc. It would be very easy to wreck your plane in what looks like a totally safe place.
Back in the 20s and 30s there was a N/S strip on the land now occupied by the EP Golf Course. I don't think you'd be able to land there, either.
You can fly into Granby on the other side of the Park, or into Boulder, Longmont, or Loveland. These would be MUCH safer options.
Eric