I'm sorry, I may have missed something here, Heidi, but does your baby have a suppressed or weakened immune system in actuality? Does she have pronounced lung involvement or a history of chest infections? If not...if you're just being proactive because she has CF, then you may be overprotective. Babies need to be exposed to germs, or they will never build up a good enough immune system to carry them their adult years. I'm not saying to be like those mothers that expose their kids to measles on purpose, but getting the sniffles a few times a year is healthy in the long run. But you know this, of course.
As for strangers touching my baby.... well, I believe ALL touching should be verboten unless permission has been explicitly asked for and granted, but then I'm so personally touch-phobic I'm probably borderline Asperberger's or something. So, yeah... strangers touching my baby? I'd be posting a big sign on the stroller: IF YOU AREN'T RELATED TO ME, THEN HANDS OFF!