This park is worth a visit if you are travelling during spring time. We visited on 19-Apr-19. We rented a car cause I love to drive. Drove from Shinjuku to the Park took around 2 hours. It is worth the ride. Or you can take a bus from Tokyo if you wanna rest.
There is a small entrance fees and any beautiful people above 65 yo will get half price. You can walk around the park, rent a bicycle or take their trains going from point to point. Each has their own track so you don’t have to worry of crashing…
I recommend bicycle and go straight to the see the Nemophi Flower Garden. Prepare to spend around 3 hours there and enjoy all the flowers and trees. There are food stalls for snacks or lunch but does not taste super good. So you can bring your food for pinic.
More information can be found at japan-guide.