I have a friend in a home game playing a Guide / Urban Ranger and a friend who started a Pathfinder Society character that was the same. The archetypes stack together perfectly fine as far as being able to have them both on a single character, but there is one issue this combo has. Urban Ranger replaces Favored Terrain with Favored Community, guide replaces Hunter's Bond with Terrain Bond. Terrain Bond grants additional bonuses while in "favored terrain" and while the urban ranger still has a "favored terrain" like ability, RAW says that Terrain Bond sits there and never does anything.
Besides the discussion of whether or not Favored Community is weaker than Favored Terrain, I see this as being a problem. In our home game we are fine with ruling that for these purposes, Community counts as terrain so Terrain Bond doesn't get completely wasted, throwing away Hunter's bond (rather powerful) for absolutely nothing. For my PFS friend, this won't fly without legitimate errata.
Seeing as all the core ranger abilities that use favored terrain get alter with Urban ranger I am betting on the side of these archetypes being deemed incompatible, but that's not my call to make.
