The park has three important sections.
After leaving the safehouse, you will enter a main courtyard leading to the park. Zombies are generally dense, but they are easily defeated in the open terrain. You may also find a medikit in the back of one of the trucks as well.
Continue up the steps to enter the park. You can either walk along the outer portion of the park or walk along the inner ring. While the exit is on the right-side of the park, you can also collect weapons near the gazebo (which sometimes includes an assault rifle.)
To the right will be an alley that leads to the security station, where you can collect some medikits that you may have used.
After the alley will be a large quantity of zombies. A single pipe bomb should take out most of them, and there are also replacement grenades within the region as well. If needed, collect one of the two new weapons, and continue to the yellow cart to the left.
The witch will usually appear in this section.
Enter the cabin and close the door behind you. Collect the few supplies there, which usually contains adrenaline. Once you are ready, open the other door; note that this activates the alarm.
Run down the alley as quickly as possible, but take out any zombies along the route. When you reach the corner, you can replace your current weapon with a long range weapon. Continue down the alleys, until you reach the ladder at the end of the central tower. Climb up and deactivate the alarm. The hordes will still continue for a few waves before they stop the attack.
You may also find weapons and medikits at the top of the tower, but the medikits aren't guaranteed.
Head to the ground, and to the right side of the gray-colored building.
The bus station is the last part of the level. Go through the darkened room to the parked buses on the other side. Clear out the dense levels of infected, before trying to reach the safehouse.