Many 'game design' courses really focus on the visual art and level design aspects of the job over anything else. If you reallyreally want to be a designer, I'd say:
1. Work on your writing and communication skills.
Even a pure level designer who just drops walls and puts down mushrooms for Mario to pick up has to be able to communicate with the rest of the team.
2. Computer Science is great for any job in this industry.
Have you tinkered around with any of the more robust level editors out there? The WarIII editor, the NWN editor? You have to be able to understand the technical aspects in order to create a dynamic game.
3. While slaving away night and day on 1 and 2, get a job in Quality Assurance.
Design positions are hard to come by. If you are a gifted programmer they probably won't want to let you transfer to design. Getting into QA will teach you a lot about the industry, the company you work for - not to mention *really* testing your resolve to become a designer.
4. Accept that your great ideas will probably never be made into a game.
Your ability to create an interesting level for an existing game is more valuable than your awesome FPS/RTS/RPG 'Darth Maul on Ice' MMORPG concept.