WINTER UPDATE:
THE CACHE IS STILL ACCESSIBLE (1/20), THOUGH YOU'D PROBABLY WANT TO USE SNOWSHOES OR XC SKIS IF YOU FOLLOW THE RECOMMENDED ROUTE (ALL OF WHICH WAS TRACKED AS OF TODAY). I DID SEE A PERSON VERY NEAR THE CACHE WEARING BOOTS, BUT THERE'S ENOUGH SNOW ALONG THE WAY TO MAKE IT RATHER HARD WALKING. THE CACHE ITSELF IS VISIBLE FROM 50 FEET AWAY (IF YOU KNOW WHERE TO LOOK!), BUT GETTING TO IT WILL REQUIRE GOING THROUGH SOME KNEE-DEEP DRIFTS.
First, although this is close to I-70, this is not a highway cache. DON'T PARK ON I-70 TO ACCESS. Not only would you miss the great hike, but you may end up with an expensive ticket. (If you insist on going that route, you could probably park at the westbound rest area overlooking Dillon Reservoir, but that might involve some bushwhacking--I haven't tried it.)
The best way to approach this is to take Ryan Gulch Road into the Wildernest area, and then take one of the many trails leading up the gulch to the south of the road. One fairly easy route is to park at 39 37.005N/106 05.496W and follow the trail to the creek (watch for some American Iron just before you reach the creek). At 39 36.620N/106 05.354 turn south, cross the creek and follow the trail (unnamed so far as I know). The cache is about 10' off the trail.
If you follow those directions, the trail is about two miles round trip, mostly level or gently downhill until the last 100 yards or so, which is a fairly steep but good trail. Our 6 year old had no problem with it. At your destination, you'll be rewarded with a great view. If you instead park near the Wildernest Center and follow the trail up the gulch, you'll be taking a longer hike and with more vertical gain, but still probably only a 2.5 or so on terrain.
Initial cache contents includes two novels for the adults, crayons and Pokemon cards for the kids, and a handwarmer and "geocone" (from the Kokopelli Trail cache near Grand Junction) for anyone.
This area will probably be accessible year-round, since most of the trails are used by XC skiers, snowshoers and hikers. But you may want to bring snowshoes. The cache is in a sunny southern exposure, so I doubt it will be buried by snow for long.
(And if you're curious about the name, our Irish Glen of Imaal Terrier fell into the creek near the crossing and couldn't get himself back out because of a steep bank where he chose to go exploring.)