I measured 8.2 miles and signs are well posted. Parking lot today(1/12/08) was clean as it gets. 5 park rangers checking $3 parking tickets made me laugh.
The "unsupervised" area got a ranger out there to take care of a jump that some rug rats had built. We took 11 bodies up early in the am a little after opening (hours are 9:30-4:00) and had a blast.
As far as the areas being snow covered or hard to traverse from an earlier post, you can always check the Sandia Ski area snow report here:
Also noticed on the way down, a lot of folks had not gone all the way up and were sliding down some of the other hills on the side of the road. They parked on the side of the road and their kids were wandering in the middle of the road. Not the safest, but surely and adventure.