Hi
I have been a number of times and anytime we asked to ride, loan or hire a bike (i.e every day!) we were told no. Apparently the licencing and registration is a problem.
Also finding your way around would be EXTREMELY difficult, the place is a rabbit warren like you wouldn't believe.
I made light enquiries into a english GPS but didn't have much luck, although i think things are improving on that front a little.
If you do find anything out i would love to know.
Mark