i lived in a dorm for two years in a double and two years in a single room in a shared apartment on campus. I brought my vest, compressor, nebs, etc and just kept them under my desk. It's pretty easy to find time to do everything, there were always certain times of day when my friends would all be in class and I was by myself. I roomed with a close friend from high school, and she didn't care if I was running treatments with her around or not. I did IVs more times than I can remember from my dorm, I just stocked up the minifridge with the bags of antibiotics! As far as sterilization, my apartment the past two years has had a dishwasher, but for my first two years with just a bathroom I cleaned with dish-soap or soaked in vinegar.
It's all up to your son though- I chose to be open with my friends about CF, so I never had a problem taking meds or doing nebs with them around. If I had chosen to go the other route, I am sure it would have been just as easy to find time to myself to do everything and have nobody find out. I will advise you to make arrangements with the college's disability services. I don't know what I would have done without their van to come and pick me up and take me to class (now I have a handicap pass and can just drive). Having a documented case with disability services also makes it much easier if you need to be hospitalized in the middle of the semester and miss some work.
You have some time though <img src="i/expressions/face-icon-small-smile.gif" border="0"> enjoy having him home while it lasts!