Café de Nuit

I would also aknowlege the oddly stabilizing factor that is Vlad Drakov. Playing on racial divisions or even forming alliances with races he considers beneath him seems WAAAYY outside Darkov's established attitudes and since non-human refugees from Falcovnia must have no shortage of horror stories I should think the general attitude of ALL in Darkon would be 'hang together or hang separately'. At least those anywhere near the Falcovnian border. Furthermore, it's not unheard of in our own history of disparate 'Racial groups', even traditional enemies, to form alliances and even certain kinds of brotherly bonds when constantly confronted by a common enemy. Nations have even been founded in this manner. Pre-colonial Rwanda for example. (if certain recent articles are to be believed) Also, with their communities swelled by said refugees, they can probably become pretty gung ho when the invasions come and there's nothing like battlefield heroism to expand peoples opinion of another group.
"I won't hear you saying things like that when those peoples infantry held off the talons long enough for the entire village of goodville to escape last year! Your Uncle and his family were in that village OR DID YOU FORGET?!! NOW GO BACK THERE AND APOLOGIZE!!! NOW!!!

An interesting thought, though let's not forget that the real thing keeping Falkovnia at bay is....
bum bum bum
the Dead.

The darkonians would be hard pressed to find martial victory for themselves when legions of rotting corpses do all of the work.

It really comes down to one factor: there is as much or as little racial tension as you need in your game. If the adventure you're writing requires some in-fighting or racist undertones then there is no reason there couldn't be fighting between the elves and dwarves of Darkon. If you prefer to gloss over the existance of demihumans at all then they sit quietly and peaceful in the background.