As in any foreign country (foreign to your experience, I mean), be careful as you don't know what it's like there.
Having been to Ho Chi Minh City recently (I think "Saigon" just refers to a downtown district there now, if I'm not wrong), you will have lots of distractions like street peddlers, street kids, touts, etc. So I'd advise bringing a P&S for street shooting, if you want to enjoy your trip and not look after your gear all the time.
Someone I know was propositioned for massage by girls on bikes, and when they touched his a**, he thought it was part of the marketing process. It was only after he got back to the hotel that he realised the marketing pitch cost him about US$100 plus all the cards in his now long-gone wallet :bsmilie: ... while the rest of us had a nice leisurely lunch the next day, he spent it at the police station making a report.