The sticker was hidden near the bottom of the Woodburn Falls Trail at Lacamas Park in Camas, WA
The sign is located on the north perimeter of the park. There are 26 parking spaces in the main lot, and more in an overflow lot.
Italian for "If landing on the other side of the road, pay attention to 6.12.015. 6.12.015 is an ordinance about sea planes. There is a sea plane base accross the street at Lacamas Lake. Zellerbach was the US ambassador to Italy.
To solve clue 3 you needed to use the numbers and letters on the phone's keypad. The first number was the key, the second number was the letter on the key. So 4|1 = "G", 4|3 = "I". When translated, the clue read "Gift of Zellerbach, east of Round".
Lacamas Park was gifted by the Zellerbach Corporation and the sticker was east of Round Lake.
Another phone clue, only this time you need to use your fingers to trace letters on the phone keypad. 713957 = "B". When translated, the clue read "Between a rock and a hard place".
The sticker was on a rock which was partially stuck in a crack in a much larger rock.
Clue 5 was released at 5:17 AM. The right and left digits of the release time are 7 and 5, or 75. Lower Falls at Lacamas Park measure 75 feet accross (left to right). The Emerald Isle is refering to Ireland, WA, to the NE. Woodburn Falls is in that general direction.