I am a very satisfied Disney College Program Alumna. I participated during the first semester of my Junior year. I would suggest working with your college counselor, who is familiar with your major, to discuss when the appropriate time would be to take a break from your studies. While educational opportunities do exist (and are required for a DisneyLand CP), not all universities will give you credit for taking these classes.
For most, the sooner you participate, the better. The Disney corporation can teach you so much, connect you with fascinating professionals, and expose you to a world of opportunities!
P.S.- when it comes time to interview, remember to SMILE! Even if you are over the phone, they can hear it!