If you don't already know, the region that pokémon ranger is set is called Fiore. Here are the towns and places:

Ring Town Ring Town is the town you start in. It has a group of Rangers led by Hayate who recruits you into being a Pokémon Ranger. Ring Town is by Raira Forest where your first Mission takes place
Raira Forest Raira Forest is just by Ring Town. In it you have to do your first mission as set by Hayate to test your Ranger Skills. There is a Pokémon lost in the forest, can you return it to it's trainer?
Fall City Fall City is on the east coast of Fiore and holds the major port of the region. Fall City has the Lucky Clock Tower in the North and has a group of Pokémon Rangers led by Joe & Aria
Summer Town Summer Town is a Mysterious Place that is a tourist spot. It is by a massive Jungle which contain many unique species of Pokémon. It also has a set of ruins. It's Ranger Union is led by a guy called Kamuri
Summer Land Ruins The Ruins in Summer Land are a perfect place for any budding Pokémon Ranger to test their skills, get Wild Pokémon to help you and just hone your skills
Shikura Mountains The Shikura Mountain Range are to the North of Fiore. At the peak of the Mountain is an ancient sacred Shrine which never opens. There are many kinds of Wild Pokémon here that may be able to help you
Win Town At the bottom of the Shikura Mountain Range is Win Town, a town with stone built houses to resist the cold. Win Town's Ranger Union is led by a lady called Erida
Beaches Fiore also has a multitude of Beaches...these Beaches hold rare and unique Pokémon Species