I would get a degree at a good school and do design on the side, that way you'll have a backup in case you decide that the design industry is not for you. I'm not sure how much experience you have, but I think you'll find that once you make a "fun" thing into a job, it eventually just becomes a job. Get an internship and try it out for 4 months. I did and discovered that it wasn't for me.
The other thing is - don't be cocky. I've seen a lot of "A" students cry over Cs in univ, and that seems to be quite a normal thing around here. It's a different environment from highschool/college and takes a lot of getting used to. Then again, I'm in the sciences.
last thing - as an engineering major, I'm obligated to inform you that liberal arts degrees are for pussies.