I would say that there are probably a few routes that wouldn't be bad. Computer Science is kind of interesting, personally I learned a lot about programming theory, while not as much about good programming practices, secure programming, and common pitfalls. I was able to pick up a fair amount of networking theory, so I guess part of choosing a major depends on what you want out of it.
Of the people I know who are doing pen testing and information security things, many of them came through other IT functions, such as networking and sys-admin. One of the great things about college is that the atmosphere of learning frequently doesn't stop at the classroom. If you can find a part time job working with an IT group or something like that and find a mentor who will help you learn more about enterprise environments, what your degree is in may not matter as much. When it comes to IT security, I think that in many cases, people are going to be looking for people with experience first, then a degree second.
Another great option is to find a co-op opportunity through your school with a local company who has an infosec team who is taking either summer students or co-ops. I've worked with summer students before and that's another opportunity that will end up being whatever you make out of it. You probably will have to do some stuff that isn't as fun but is something that needs to be taken care of, but walk in and do the things that you're tasked with and show that you know your stuff and then suggest things that you'd like to be involved in. If you show that you are capable, those folks are probably going to be good references for you both technical and employment wise in the future.
The biggest thing is though, college isn't just about the classes. You have a whole lot of resources at your disposal as far as professors, staff, and other bright students. Make the most of all of it, and don't forget to have some fun along the way.
CISSP, CSSLP, MCSE+Security, MCTS, CCSP, GPEN, GWAPT, GCWN, NOP, OSCP, Security+