To be fair, there could be numerous explanations to it, all of which didn't really seem worth putting in the comic as they're not particularly funny.
For a start, just because he can't read doesn't mean he can't recognise the odd word. Add that to the fact that, even if you can't read, you should be able to recognise shapes, so if the bar name is written on the paper, AND above the bar, he'd be able to compare the symbols and find the bar.
Then there's the fact that there's a whole city of other people, who could read some of the details, direct him, or whatever. If there's a job centre they could state that there's a vacancy at the Leafy Bar.
Alternatively Shelia may have people on the streets handing out the flyers, stating that there's a job vacancy. Vas could've taken one of the flyers (not being able to read what the job was) and ask for directions to wherever it is he needs to go.
You may've noticed one similarity between them though - they really wouldn't provide much entertainment.