I've seen a few times now in pictures that on major roadways, there are green (or blue in Europe) signs along them. I tried to locate some in my sim but couldn't. Is there a setting that controls this or some kind of add on?

You need to set object autogen to one of the higher settings. Sorry, on my phone at the mo, can't check exactly which one...

Scotchegg's right; try increasing your "number of objects" under Settings > Rendering Options. That should get road signs, traffic signals, etc. to show up.

Thanks much!!