I'd recommend Jade Emperor Pagoda - wonderful city. See http://answers.worldnomads.com/questions/viet-nam/2265/what-are-some-good-things-to-dosee-in-ho-chi-minh-city about 8 years ago
You can get a tour to the Cu Chi Tunnels, which will take you out to the tunnels and you can fire some weapons if you like. I think t is about 70,00 Dong for entry, you will pay a bit more for the free video presentation if you really want to watch it although it is just full of propaganda and not much factually correct information!
Once back in HCMC you can sample some street food or go to the Ben Thanh night market? There are plenty of pick pockets and scammers as you would expect from any night market in SE Asia, but it is perfectly safe if you keep your wits about you. almost 8 years ago