By the time you pay for preschool/daycare, you can pay for a nanny/sitter to come into your home and play with your child one on one, teach colors and letters, take to the park, museum, and even playdates. And the exposure to bacteria and viruses is limited until immunities and strong lungs have had a chance. I know I posted that same suggestion already but I'm glad to see so many others chime in on the same line. That is the approach we took. Our 9 year old has only been hospitalized for one tune up, altho we've had surgery for polyps several times. Out CF Clinic recommended he stay out of daycare as long as possible when he was born. So we brought in nursing students, elementary education students, and similar people throughout infancy and toddler hood while we could. He went to only one year of daycare, then half day preschool, and kindergarten. He's had no trouble socially or academically. He does well.
I also believe there are several studies that suggest most children (not specific for CF) do better overall, socially and academically, if they stay at home until preschool and kindergarten age. But that's a whole different debate which you can research to make you're own conclusions!