He watches them walk away and briefly considers making a break for the wall himself, but ultimately follows when he remembers that on the other side of there be werewolves.

Raph is not overly fond of werewolves.
And even if he was, fixing the car is way more preferable than having to deal with that mopey stalker and the potential of another Stiles.

He stows his sai and slowly follows Grace and the kid back to the Jeep.

Teenagers are exhausting.