A lot of the super popular street food vendors are probably not serving bacteria ridden food because if their patrons got sick, they'd stop buying food there. A lot of the street food vendors have tons of regulars lined up to buy. That's why you kinda want to ask where the locals eat.
Plus the way a lot of it is cooked (in hot oil) and then handed to you, the bacteria would not survive the cooking process. The popular ones that are popular with the locals and get great reviews probably have it down to a science. They probably know how much meat to order, keep in on ice, etc..
At least I hope!
There's a cool channel on YouTube called the Food Ranger where he eats a lot of street food and also food at small restaurants in Asia. He's from Canada and is married to a Chinese woman.
But yep food safety is important. I saw a news story that some refrigerator food trucks in the USA aren't safe. All those trucks (including the big rigs) that are supposed to be kept at a certain temp.. Sometimes the fridge units stop working, and they just deliver the food that may have sat in a hot truck for days. Or the drivers will shut the fridge units off to save fuel. So if you ever get sick making food that you yourself made at home, that might be why. And there aren't enough police and inspection stations to catch them. Some get caught and cited.