Easy to get to. Parking does cost a few dollars though unless you park down the street. The hike does get a little muddy toward the end, so break appropriate footwear. I felt bad for the people that walked for about 45 minutes, then had to turn around. Also, if you have very small children this isn't the walk for you due to how muddy and slippery it is toward the end.
The walk is about an hour each way at a moderate pace. Besides the parking fee, there are no fees here.
Bring plenty of water, besides the gift shop near the parking, there is no other place to buy any.
May I also recommend I love yogurt down the road near University of Hawaii, Manoa. The Dole pineapple yogurt is amazing.