I would say don't go out right and say you wanna just smoke pot. Go, and say you have bad anxiety (or what ever you have), then take what he perscibes, then wait a week, and set a new appointment saying that it didnt work, and you would like to try something else, then in a week or so call him, and say it isn't working, then get a 3rd perscription take it for a month, tell him it seems to be a little better, then after the month is up call him to set an appointment and say its bad again...then offer your idea on smoking mj
You gotta be sly like a fox, if you go out right and ask he probably wouldn't perscribe it to you....ever.