Ho'okipa Beach Park is located right beyond Pa'ia and Ka'au town makai (toward the ocean) on the Hana Highway.
You'll pass the steeply graded exit before you pass the entrance, so be looking for the sign marking the spot. There are two very different spots (hangouts) located inside small Ho'okipa Beach Park: one is an overlook that is almost immediately to your right once you turn into the park, and the other is the road that leads down to Ho'okipa Beach itself and then back up to the exit you passed prior to turning into the park at the sign.
Ho'okipa Lookout is a nice spot to get a good view over parts of coastal north west Maui (to your left) and the Pacific Ocean stretching to the north in front of you. It's also a great place to watch surfers and windsurfers catch the waves below you on Ho'okipa Beach. World-class windsurfing events are held here annually. After you're done at the lookout, your best bet is to get back on Highway 36 and continue your journey. You don't want to waste too much time at this location. Also the beach is a surfer's hangout, so the crowd is not always as full of 'aloha' as people in other parts of Maui. We've never had any problems, but there are better beaches on Maui, so why waste your time here?