i don't think you want to turn off either the exhaust or intake fans. it might be best to go ahead and grab a dehumidifier.. especially if your to be adding to the room, as I'm sure you'll want to later..:rauch08:
any 60 or 70 pint dehumidifier will work perfect. there are presets but you will need to play with it a bit to find what works for your setup.
hope this bit of info helps.. I'm sure there are some locals from diego who kan give a little better insight..