It can be good and bad. I'm 27 now and growing up with CF I myself have found at times that no one can understand what its like on a day to day basis, especially when times are tougher. For the most part I have lived a healthy life and only in the past year or two have I run into greater struggles. Like I started out saying though, there can be postives and negatives to interacting with more people with CF. On the good side you can share your similar experiences, seeing that there are in fact others that are going through the same trials and tribulations you go through. Interacting directly with other people with Cf can be iffy, from a bacteria perspective not only could you be exposing yourself to harmful bacteria they may have, but also you could be exposing them. The most obvious physical risk if he was looking at directly interacting with other CF patients would be to make sure your boyfriend is neither MSRA or Cepacia positive and that the CF patients he does interact with are not either. I'm not sure how strict they are on this in other places but at the hospital I go to they are very careful to keep patients separated especially those that are MSRA and Cepacia.
Since you asked I will say that for myself it was almost more painful than pleasant. The first time I had to stay in hospital I was 14 years old and staying in a teen ward at the local children's hospital where there where a number of other CF patients. On the good side the other children with CF were very helpful towards me, most were aware it was my first stay and did there best to help me, and I'll always remember and cherish that fact. However, in the grim reality side of things, of the 8 CF patients that I met in that stay all have since passed on which was a very difficult thing to deal with.