Honestly, as long as a doctor/nurse doesn't come in their scrubs from the hospital, the chances of them carrying MRSA is pretty unlikely. Keep in mind that pseudomonas is in tap water and staph is on every surface including skin, EVERYWHERE!! You can't avoid these bugs. I know that is panic attack inducing, but you just have to come to terms with the fact that it is there. You should of course do regular hand washing and take precautions, but people with healthy don't culture these bugs for a reason -- the bugs don't like to live there. If a CF person's lungs are a good environment, the bugs will find their way there.
Focus on the things you can can control and try not to let the ones you can't control ruin your holidays. As long as your health care worker friends use good hygeine they are no more risky than anyone else you have over.
