I have been working in Taiwan for 2 years now...I worked at a cram school and you do have to sign a contract. But...many people break that, a) if they find out they don't like it b) only planned to stay 6 months (like you) c) find another/better job. It's not that great for the school for you to break the contract, but it is possible. You might just lose out on a bonus at the end of your contract or your flight back. It is still worth coming and trying it out. It's a great experience even if you only plan to stay 6 months. I think that's long enough to see what teaching in Asia is all about.
Good Luck...