Will I still get to go to all the businesses (such as Microsoft and Ernst & Young) even though I am not in classes?

Sure, you can tell the intern site Director in advance what days and times you would like free so that you can attend the site visits. However, most interns find they would rather stay at work because the internship sites provide quite rewarding work. However, I would get you the full schedule in advance. You would also want to take off for Vienna and the overnight trip to the medieval village.