so are you asking how to maintain your exercise, which i assume forms part of your diabetic control....?
from what i have heard from a colleague who had it you would need to take it easy i think, mild activity should be sufficient though, like walks etc....
is you current gym activity making a significant difference to the diabetes? can your diet not do most of the work?
as i say, the details of bells palsy is unknown to me, so i wouldn't know what levels of activity would be comfortable...