There are many buses that ply the roads between Mui Ne and HCMC, but I’d recommend taking Futa Buslines’ Phuong Trang (link to Vietnamese-only site) bright orange buses, one of the more reliable bus operators. It's a bit longer than the many tours that leave the backpacker area, but it’s safe and they stop for food half way in. For your 130,000 dong ticket ($6.25) you’ll receive a bottle of water and a fresh towel.