[quote=@Saquira]
The way I figure it Fridolf is only likely to already know the signs if he's previously worked in the city, but if he hasn't he might be aware of someone he could talk to in order to learn them.
[/quote]

I was going to work on a similar assumption, in that he's aware of of Glosseghar as they probably have similar counterparts in the other cities/towns he's visited in the past, though each criminal institution create their own symbols, and as such he doesn't actually know what any of the specific signs mean in Telchar.