If you're playing the original Demo, there is no recording of what appears where. But if I remember correctly, Ralts appears on Route 4, and Gastly & Weedle appear in Grim Woods. Treecko, Mudkip, are not available in that version, and you can't get Gible unless you started with it. Dawn Stone is not in that demo either.
The Battle Frontier demo has all those Pokemon, though!
The Battle Frontier demo has all those Pokemon, though!