My Garmin GPS easily took me to Cronin's Yard, 15-20 min from downtown Killarney.
2 Euro coin to park.
With clear weather, the Devil's Ladder route is obvious. Go through a gate following a signed "loop" trail, which is more like what we would call a fire road in the States. Highly cobbled at times. I was worried about stream crossings based on the parent page (last updated 2008 as of this writing), but this is not an issue: there are two big metal bridges at the lower stream crossings and huge stones across the third. From the lakes, the trail starts to spiderweb, but again the destination at the base of the Ladder is straightforward. The climb through the Ladder is Class 2 scree with no apparent preferred route. Again straightforward destination to the top of the saddle. I think the danger on the Mountain Rescue site is overstated; there are certainly a few places where a slip or dislodged rock would be suboptimal, but the most dangerous part of the trip is the approach to Cronin's Yard with oncoming traffic on a road the size of a driveway.
From the col, spiderweb of trails to the big cross on the summit.
I took 4.5 hours at a casual pace. There were a fair number of people on the route, even for midweek. An early start might help avoid crowding issues in the Ladder. This is a highly recommended hike if you are in the area.