Hi Gmanon2weels, the Hw1 is very noisy road. The most interesting section of it is from Nha Trang to Hue. From Saigon to NhaTrang I suggest you should chose the road along the beach which has more view and less traffic. Saigon - Long Khanh - Ba ria - Binh Chau - Lagi - Phan Thiet - Mui ne - Bau Trang - Phan Ri - Phan Rang (Hw1) - Vinh Hy - Binh Tien - Cam Ranh - then follow the new road named Nguyen Tat Thanh to Nha Trang.
It will take you about 20 days easy ride from SG-HN. One of my friend just did it last mounth in 13 days HN-SG.
I'm in Saigon. So, if you need any futher information just let me know. Or you can contact me on FB. https://www.facebook.com/phungnamthang be cause i not offen in bikeforums.net.
Regards.
Victor.