I would never take a dog for a walk on strange ground until all parvo shots have been given.. It just would not happen with me for whatever reason...
I usually scare the hell out of people about parvo.. once you have had it or know some one did that... you certainly change your feelings.. if it costs like $1,200.00 or more to save a puppy that gets parvo..that is if the puppy lives, we need to just ask ourselves is that walk worth it.. then we need to make a decision..
This is only my feelings on this subject..