Depends where you're going and who you know.
With the instructor hat on, always request PPR for every airfield, or at least, try to get PPR - Gives the student an idea of what to expect.
With my "jolly" hat on, I know a number of airfields that'll take me with no issues at all with or without a call on the radio. But then, I do know who operates the airfield/strips and normally places I wouldn't take most students.