As a long time stutter-er as in about 60 years, I have had a PPL since 1972. I have tried many and varied ways to rid myself of the impediment, although nowhere as bad it is still there, particulary in times of stress, but not always. DO NOT let any thing stand in your way of acheiving what you want to do. I had a couple of very understanding flight instructors, and spent many hours with them practicing radio calls in a link trainer. I over heard one day another instructor having a grizzel about the 'quality' of students the club was getting and to quote" they even let that silly bast--d XXXX in who can hardly say his name propely" so that made more determined to pass my flying test. Eventualy I got better at the radio, even had the tower ring the club and ask who was opperating the radio for me---solo flight. I now have an Amature Radio Opperators Certificate of Proficency for ham radio, so as I said at the start, go for it--do not ever give up. Good Luck!