There are several ways to get to Quy Nhon, either by bus, car, or airplane. Quy Nhon is about 650 km away from Saigon and I recommend taking the flight over. It takes only about an hour by plane from Saigon to Quy Nhon. Vietnam Airlines has a daily flight from Saigon. There is only one flight daily to and from Quy Nhon. If you wait to get to Vietnam to purchase the ticket it is only $33 one way. However if you purchase the tickets in the US the price is $88 one way. The flight is rarely booked completely so you have the luxury to wait. Their phone number in Saigon is (84 8) 832 0320 or in the US its 1-415-677-0888. While in Saigon, if you aren't close to a Vietnam Airlines office, the other alternative is to buy your tickets at the Sinh Cafe in the backpacker's district (address is 246-248 De Tham St., District 1, HCM City, Vietnam, telephone (84 8) 836 7338).The price will be the same as at Vietnam Airlines.
Furthermore if you take the flight, you get to see the magnificent scenery around Quy Nhon. Quy Nhon is in the southern most part of the central highlands so the landscape changes dramatically from Saigon. Quy Nhon is a coastal city with lagoons and mountains.
Around Quy Nhon you will find that traffic isn't as heavy as in Saigon. Also you will find many more cyclos and the drivers are really sweet and nice, unlike the pushy ones in Saigon. So if you feel the urge to pop onto one of these bad boys, I suggest you try it in Quy Nhon rather than in Saigon where the drivers can often times be nasty.