The braille message tells you to wait. Wait for 2 minutes. Regice dwells in Island Cave at the West side of Route 105. You need Surf to access.
In the South part of the Desert on Route 11 there is a small cave you can enter. Go in and in front of you there should be a wall inscribed with Braille press "A" on it move to the right twice and twice down.
Go to Route 120 and you will find a cave called the Ancient Tomb. You will find the Braille code inscribed in a wall. The message tells you to stand in the middle of the room and use Fly. After you do a door will open which allows you to catch Registeel