JeJu Island

There are 2 main cities on the island. One on the north (Jeju city) and one on the south. The northern city is divided into two chunks, the new part of town and the older. In the middle is a downtown with loads of places to eat drink and womanize (I only mention this because there seemed to be more here than in Thailand!)

The southern city is also kinda divided into two cities, one has a few sites like the bridge park, the other has the falls. The Eastern city on the south end has a hotels and hostels for around 30,000W.

Mt. Hallasan is doable without a guide and there are 1,000 of signs and many different routes.

To answer your second question, you definitely do NOT need a guide for Hallasan. If you're in decent shape, it's not too difficult at all. If you do a search of Thorntree or search my previous posts, there's a lot of information and advice on here about climbing Hallasan.

Jason