Is food from street vendors safe for westerners?

In The World Of Vietnamese Street Food, Pho As We Know It Only Scratches The Surface.

What list of Vietnamese cuisine would be complete without pho?

It's almost impossible to walk a block in Vietnam's major cities without bumping into a crowd of hungry patrons slurping noodles at a makeshift pho stand. This simple staple, consisting of a salty broth, fresh rice noodles, a sprinkling of herbs and chicken or beef, features predominately in the local diet -- and understandably so. It's cheap, tasty and widely available at all hours