Sometimes, the best way to hide something in plain sight is to call attention to it. You could place some of your main governmental buildings around the central triangle and call it the the three-corner forum or something. The roads that lead out from it could be named as being points on a triangle. Instead of noting the larger surrounding triangle, instead point out the arrowhead shape made when ignore the bottom segment in favor for the two connecting to the central triangle. Don't tell anything as a whole, but point out all the elements. If you aren't working to hide them, they aren't important. Instead this is happy shape town/etc. That'd likely take care of them noticing the overall pattern while they're there.

Also, what about drawing the overall city map from a different angle or trying an isometric map? That would obscure a lot of the connections and pattern without you having to change too much. Then, instead of providing an overall map, make small neighborhood maps. If you do the smaller maps at different scales, it'd be difficult for your players to put them together.