This park is a great place to go if you're not a beach person. From Wailea it's less then a 30 minute drive. Parking is $5 and there were lots of paved parking spots. There are portable toilets, that were very clean. If you don't do the "secret trail" you'd probably only need about 30 minutes to walk around and see the Needle, take pics etc.
However if you want to spend the morning or afternoon here go up the paved steps to where there is a small hut and look out point directly in front of the needle. There is a sign posted on the left hand side by the railings saying "stay on marked path" and what time the park closes. Cross the railings and walk up and your now on a well maintained hiking path. Clearly people have been walking on this path as it is well maintained.
We only spent two hours hiking on the trail as we also wanted to hit the pool in the afternoon!! We bumped into only 6 people whilst hiking. Seemed like locals also know about the trail.
There is something at the end, a Temple of sorts. We didn't get there, but the hike had us walking through the rain forest, crossing small streams and we got some amazing waterfall views.
Only do this trail if your a regular hiker and you have the right sort of footwear.