well thats part of it but that just opens the chocobo ranch not the chocobo ruins. The ruins are under the chocobo ranch.
This is how to open the chocobo ruins;
Have dispatched all 5 levelson successful treasure hunts, at least 3 times for each level.
Have raised your 4 choco-runners to level 5.
Clasko will then ask you about a hole he found. That the entrance to the ruins.
Down there you will find;
An amazing chocobo right at the end of the ruins
The boss-the Anything eater just before the amazing chocobo
2 shining Gems
1 Pixie Dust
The Machina Reactor for Rikku to learn for her special Dressphere
1 AP Egg
2 Mana Springs
1 Mega-Phoenix
1 Cats Bell
The ABC of Repair key item to fix the machina boss in chapter 5 at Djose Temple
2 Stamina Springs
2 Mega-Potions
2 Blessed Gems
1 Mythril Bangle
1 Rune Bracer
2 Turbo Ethers
1 Wizard Bracelet
and 2 Poison Fangs
And thats your lot