I'm always positively surprised by how much Vietnamese appreciate it when you at least try to speak some words of Tieng Viet (Vietnamese). I picked up some over my years here and I always start the conversation in Vietnamese, not in English. We are in Vietnam, right? In return they will be very forthcoming and helpful, and laughing their arses off at my pronunciation (and i gladly join them in that). Ice broken. Give it a try, you'll see!