If your goal is truly focused completely on starting a tech startup after completing your degree, then you should be looking for:
1. Location. Go somewhere where you can find and meet like-minded people and the resources to help you get going. San Francisco, NYC, Boston, Chicago, maybe Austin. Cities with established startups and college towns are both great for this. PG conveys similar opinions in his essays about startup hubs.
2. A good CS department. You'll need fellow developers. Mine them from a good CS department.
3. Being in a school that is known to generate lots of startups is certainly helpful. Think Stanford, Berkeley, MIT.
Keep in mind, this is coming from someone who spent 3 semesters at Rice (before transferring to UT Austin).. It's a great school, but I would not choose it as a place to get a startup kicked off.
I'd also like to backup tsally's comments about large vs. small CS programs. This is the primary reason why I left Rice (although I was EE, not CS). The school is too small and the CS and EE programs did not offer the breadth of topics that the larger schools do.