I do agree with MovingIn07. When I moved to HK in the mid of June, I kept the window opened. The result was the whole floor was wet. Three or four days later my bedroom's ceiling got mold. After that I try not to open the window, it is worked, no more mold. However, I still prefer to open the window to get more fresh air. That why I think I need to have a dehumidifier to turn on it when I leave my room for work.
Jusco and Apita often have good deals on the Japanese brands. I saw a few Mitsubishi ones there last week at Apita if you are still looking.
I am looking for a used one if anyone is selling. Thanks.
Check the various classifieds forums- dehumidifiers appear all the time.