Look on the map, you ding dong T_T
Emerald Valley is the place right after Flowerain Town. It's neither a town nor a route, it's a valley. As I said, the places won't be as black-and-white as they were in normal pokemon games. It's not just "Town, City, Route". Anyway, to answer your question, it's more of the outskirts of Flowerain Town. It is what it says. It's just a small, emerald-hued valley with a few inhabitants.