If the Zodiac Killer had entered the park here, it is highly unlikely he would have backtracked in a westerly direction towards the crime scene. An escape route north on foot to escape the park would have been extremely time consuming. The detail given by the Zodiac Killer in his November 9th 1969 letter (if true), suggests that once he entered the park at Julius Kahn Playground he headed east, where in the wooded section opposite Laurel Street, he observed dogs that never came within 2 blocks of him, because they were to the west. Two blocks west was Julius Kahn Playground, where "seven of the best search dogs in the country, gathered at the front entrance of the Presidio". The Zodiac Killer's claim in his letter was correct that dogs were assembled by Julius Kahn Playground, but this detail had been released in the San Francisco Chronicle newspaper as early as October 15th 1969, which stated "A large contingent of police with dogs and searchlights secured the area around Cherry Street, which included the wooded south boundary of the Presidio and Julius Kahn Playground. So any escape through the park in a westerly direction, two blocks towards Cherry would have been highly unlikely.
If the Zodiac Killer had continued eastwards through the park from the wooded area opposite Laurel Street, he would have reached Presidio Boulevard, where police motorcycles would have been traveling from the "south to north west" (see map below). The two yellow circles on the map show two positions exactly 150 feet from Presidio Boulevard, so if the Zodiac Killer was at either of these locations he would have been in prime position, nestled in the woods, with the ability to observe motorcycles traveling along the roadway, and ready to escape from the park to the nearby Lyon Street, which was 370 feet from Presidio Boulevard.