GoBay (www.hbrc.govt.nz) local buses (fitted with bike racks) run many times daily between Napier, Hastings and Havelock North. Napier to Hastings (adult/child $4.20/2) takes 30 minutes (express) or 55 minutes (all stops). Buses depart Dalton St bus stop.
See www.rentalcars.com for car-hire deals with companies at Hawke's Bay Airport, including the big brands and local outfits. RAD Car Hire is also at the airport.