You can access the cache from the Bray to Greystones cliffwalk. Around the given co-ordinates where the wall ends and the metal rail starts you will see a rough path - follow this down.
I recommend doing this cache in conjunction with Brunel's Folly, which is located nearby
This is a high terrain cache and not recommended for young children. I have rated the terrain based on the the conditions in winter where the descent could be wet or icy. In summer when the ground is dry you can knock a star or more off the terrain though. However, if you don't feel comfortable when you get to the start of the descent don't do it. It's only a cache!