Blind people know where to go. They know turns on walking routes and the numbers of stops on bus routes. The dog then learns the route by repetition, much as it would any other action. There is also lots of mobility and handling training carried out at the beginning of the partnership, based on the owner's more regular journeys.
Mind you, when one of my older students once turned up late to a college class, he blamed his dog. Sometimes they would go to the bus stop via the post box - a longer walk for the dog, but a journey his owner would allow extra time for. On this occasion, the owner firmly maintained that the dog had deliberately taken him via the post box in order to get a longer walk. Apparently his dog did this quite a lot.