The north side is considered an urban natural reserve, so please walk only on trails and be careful not to step on flowers and animals, like turtles, snails... Better to come here during the day. Terrain is hilly with potential steep inclines, depending on the path you take.
Currently there is a mega construction work taking place on the hill, so the easy access to GZ from the garden itself is blocked, as of march 2017 and probably for the remainder of 2017. Otherwise the terrain would have been 1.5. You will need to climb from Tzel HaGivaa St. where the crazy houses are. The shortest route is straight up but the hardest. I recommend figuring out a more moderate route that eventually leads you to GZ from the east side. The view is well worth it, on a clear day you can see a panoramic view from the sea to the hills of samaria. BYOP