The "Lover's Jump Stash" is located somewhere near Lover's Jump Creek, which has it's basin in the Wahroonga area. There are several ways to get to this place but you should be aware that once you arrive at the search area gettting a good clear reading on your GPS is going to be tricky. I spent almost a hour trying to get a solid fix.
As a precaution I have included a spoiler in the encryption hint below, so beware and don't decipher it unless you really are stuck.
There is lots of wildlife to be seen along the way. I saw a Kangaroo, various Lizards, Fish, Black Cockatoos and beautiful Flora. During the summer months, if your hot or thirsty, the water in the main creeks might be ok to swim in but only drink from the side streams further down river.
Backtracking is way to avoid Park fees, but either way you should allow 3 hours for this cache.
Good Luck