Ha Long Bay is one of my first choices to quickly satisfy a Vietnamese craving attack which, like a ninja, comes fast and furious. While I appreciate the Vietnamese sub and other delights, I am fiend for pork and spring roll vermicelli noodle bowls (number 41 on their menu).
Chosen mainly for convenience (it's about a block away from my office), I can't praise the decor or the atmosphere; I usually get takeout to avoid being seen under the flourescent lights. And I will admit that there are probably better Vietnamese places around. But this is a quick, cheap, eat-at-your-desk lunch option for someone on the go.