Visited 23rd March 2003: We visited Penmaen-Gwyn after spending an hour or so at Strata Florida Abbey just down the road. The stone stands on a small hill just north of the road (south of the forestry track, contrary to the impression given by Multimap).
There's a picnic place nearby, but also ample parking at the bottom of the forestry track. The boys were asleep when we arrived, but the stone is so close to the road that there was no problem leaving them in the car. The sunlight through the trees was beautiful, and we took the opportunity enjoy the place in a strange child-free quiet. Very pleasant.