Vaci street is safe all around the day and evening. Either you are walking here early morning, or late in the night.
The street has been a calm walking place for tourists and kept safe from any kind of unfortunate accidents.
There is no street crime reports as the area is heavily monitored.
However, on crowded days, you should be careful from pickpockets, like any other touristic city.
Vaci utca definitely comes with scams for tourists,which can be avoided if you are aware.
Common Budapest scams Vaci street involve the following.
On a couple of points,A guy asking you to come inside an adult bar,which may charge you hefty money.
Some pedestrians offering you cheap iPhones or perfumes on 1/10th of the price.
Two girls asking for direction and trick you to visit a bar,where the bill is around 500 Euros or more for the coffee.
Although currency exchanges at Vaci street are having poor rates, you can be scammed by people standing nearby offering your lower rates and giving you some other currency than forints.