There are at least two ways to approach this cache. The longest way (might take about 30-40 minutes one way to the cache) is to park along Upper Sumnervale Drive and go directly over the stile at the end of the road into Greenwood Park. Follow the uphill track that leads to the Scarborough Bluffs Track at Evans Pass Road. Be careful crossing Evans Pass Road and look out for fast downhill cyclists and cars. Do not park on Evans Pass Road as there is no parking available. Continue uphill on the Scarborough Bluffs Track which starts across the road and after a few zigzags watch out for a small sign which says "walking track to Taylors Mistake 2.5 km". Follow this track and have fun finding the cache. (note: if you continue on the Scarborough Bluffs Track from this turnoff it siddles all the way up to Evans Pass itself and it will then take you a very long time to get to the cache site).
Alternatively, drive up to Evans Pass and along the Godley Head Road and park near S 43 35.048 E 172 45.857 and find your way from here. This is a longer drive but a shorter walk.
The views from the cache site are superb and this is a fantastic Port Hills Walk to enjoy.