As soon as you climb down the stairs just to the west of the start of the route, you'll run into Sina and Dexio, who will power up your Pokédex to enable the Coastal Kalos Pokédex. Pokémon that you find on the next couple of routes and areas are all considered to be in the Coastal Kalos Pokédex, meaning you'll find quite a different variety than the ones earlier on. They are also numbered #001-150, just like the Central Kalos Pokédex, so don't get too confused with the numbers now!
Anyway, head up and then to the east to pick up a hidden Super Potion in the rock just above the entrance. Head back over to the west and then jump down the ledges. Try to hug the western side as much as possible, jumping down until you eventually find an HP Up by a set of ledges. Grab it and then jump down the ledges to the right and you'll wind up where you would have if you went south from where Sina and Dexio were, through a patch of grass.
Don't worry about that patch of grass, as there's more grass just to the south for you to find some new Pokémon in.
|Wild Pokémon on Route 8 (Upper)|
||7 (Horde)||Commonly appears in a horde (5x Wingull)|
||14-15||More common in the normal grass.|
|Can appear in a horde (4x Zangoose, 1x Seviper in X; or 1x Zangoose, 4x Seviper Y; will attack the opposite)|
|Can appear in a horde (4x Seviper, 1x Zangoose in Y; or 1x Seviper, 4x Zangoose in X; will attack the opposite)|
|More common in the Yellow flowers.|
|More common in the normal grass.|
|More common in the Yellow flowers.|
|Can appear in a horde (5x Taillow). Rare.|
Right at the start of the tall grass is Rising Star Paulette, who uses an Axew L19 on her team. Watch out, as it has Dragon Rage, which will do a fixed 40 damage — a LOT of damage at this point in the game! Fairy-type Pokémon are the way to go against it, though.
South of her you'll find a boulder you can't move just yet — you'll need Strength from the second Gym in order to move it — as well as some steps leading up to some yellow flowers, which are more likely to have Pokémon such as Absol and Mienfoo. There's also Rising Star Rhys in the flowers, with a Pancham L15, a Skiddo L16, and a Goldeen L17.
Further south of Rhys you'll find some steps. They'll take you to a fork in the road, where you can head either west or south. Heading west leads you to Black Belt Cadoc with a Machop L20. There's a hidden Escape Rope near the edge of the cliff.
Head south instead and you'll find another patch of normal grass with some rocks you can jump across to further south of that. There are three points where you can hop across the rocks. The topmost path will eventually lead you to Ambrette Town, but wrap around the west and you'll find two other sets of rocks you can jump over to. The top one leads you to a Leaf Stone while the bottom leads you to a dead end. Grab the Leaf Stone, then head back to the rocks directly south of the patch of grass.
To get to Ambrette Town from the rocks directly south of the grass, just hop east one, south five, west one, then just south all the way. If you want to fight a Sky Battle, from the topmost rocks, hop east one, south three, and then east one to find a Sky Trainer. Sky Battles can only be fought by most Flying-type Pokémon and Pokémon with Levitate (not everything, though). If your Pokémon doesn't look like it's flying in battle, like Farfetch'd, it won't be able to participate in the battle. Sky Trainer Howe uses a Drifloon L15 and a Pidgeotto L18, which is good news if you have solid flyers, but bad news if you've only got a Fletchling you just put in your party and haven't bothered training yet.
Assuming you've taken the correct path, you now only need to head south in order to reach Ambrette Town. You can also hop down the ledge to take a shortcut back north should you so desire.