Dropping from Haleakala to the coast is on my list but I haven't done it yet.

There's only so many paved roads on maui.

ride the main roads back to the Pilani Highway. from Kula you can take either Omaopio Road or Holopuni Road--- turns into Omaopio/Pulehu Raod to the 350, the mokulele highway in the central region, and back to the beaches.

or you could try and find a more direct route.

I've got the best agricultural map of the island right here, and the only direct drops back to Wailea from the Kula Highway look like 4WD jeep tracks, doable with a cross or mountain bike. there's a few of these marginal roads worth exploring on a cross or mountain bike between the coast and the kula highway.

If you're staying in Wailea, do an exploratory with your car and check out: Kamaole (aqueduct) Road and the road inland from David Malo's Church and behind Silversword Golf Course. you might be able to ride the 370 to waiakao road, or down directly from rice county park on the Kula Highway, but i suspect that is going to be dirt roads.