The first question is whether you need a motorbike at all. If your plans sit inside the city — Tran Phu, Po Nagar, Long Son Pagoda, Hon Chong, Dam Market — walking plus ride-hailing will be cheaper and less trouble.
A bike earns its keep when you head out of town: Doc Let, Nha Phu lagoon, Dien Khanh Citadel, or a run down Nguyen Tat Thanh boulevard toward the airport — that coastal road is genuinely beautiful and the best single reason to have your own wheels.
Before you take the bike, check brakes, tyres, lights and horn, and photograph every existing scratch so the handover back is not a negotiation. Ask which fuel it takes. Insist on a proper helmet, not a thin plastic shell.
On paperwork: foreigners riding in Vietnam need an appropriate recognised licence. Plenty of rental shops never ask, but that does not make you legal at a checkpoint or after a crash — travel insurance routinely declines claims where the rider was not properly licensed. This is worth taking seriously rather than treating as a formality.
Never leave your passport as a deposit. Some places ask; you should decline and offer cash or a photocopy instead.
Traffic here is gentler than Hanoi or Ho Chi Minh City but still takes adjusting to. Take most care at the evening rush along Tran Phu, and at night on the unlit coastal stretches.