Taxi rates?

I gave up on trying to pay the "authorized" rate last year. Couldn't find a taxi driver who would quote the authorized rate or who could find a rate card in his vehicle. Very unlike Patzcuaro where there is never a question about the rate NOR do you have to ask and agrees on a rate before you get in cab. Must be a difference in culture. Also, most of the time taxi's here have change but it is still a good idea to ask.