Regarding my earlier statement of the races on the cover ...
I have not kept up with all updates on what 4e will be like (as, for a while, it seemed to change week to week - sometimes seemingly contradicting earlier statements), so I had not yet seen the dragonborn pics. However, when I looked at the cover of the PHB, I noticed a male with horns, scaly skin, and a reptilian tail, and so I presumed he was dragonborn. The female, on the other hand, looked mostly human except for two small horns on her head, so I presumed tiefling (as in 3e tieflings were said to have only one or two minor features that betrayed their nature, the better to slip unnoticed amongst humans). I realize my mistake now. (Although I still find it hard to view those things on her head as anything other than little forward pointing horns.)
That said, I am becoming more confused as to how WotC expects mixed settlements to exist in PoL setting. Tieflings that look mostly human could fit in without much trouble. They look human enough that hair-trigger fight / flight reactions are not going to be triggered upon seeing them, and if the townspeople get to know them first, they may not attack or flee even if they learn of the being's fiendish heritage.
But a tiefling that looks like a fiend recently raised straight from hell through some horrific evil rite is another story. At least elves, dwarves, halflings, and gnomes look mostly human. 4e Tieflings (and Dragonborn, for that matter) look more akin to the trolls and lizardfolk that bedevil their little flickering point of light settlement and slay those that wonder into the shadows around it. Even shifters and changlings (in their true form) look more human than these monstrous appearing tieflings and dragonborn.
In 3e and 3.5e I've often had (half-) orc characters - PC or NPC - treated with extreme suspicion if not outright hostility by whatever settlements they enter. Lizardfolk, half-dragons, half-fiends, and so forth were often treated far worse - from the minimum of refused service to at times being driven out of time by a blood-thirsty mob.
These races - the dragonborn and the tiefling - will similarly be viewed with unfriendly and even hostile attitude by most they meet. They simply look too monstrous to be trusted, and in a Points of Light setting this is even more true than in a more cosmopolitan and mixed setting.
Consider the following:
In a small self-sufficient town, built near the ruins of an ancient and tumbled castle, there recently came about several disturbing occurrences. A couple small children have disappeared while wandering near the edge of town. Strange death-pale wavering lights are at times seen in the woods - from the direction of the tumbled keep, but they vanish soon if followed. Rumors are starting to spread that some evil cult is perhaps at work. Perhaps signs of a cult once thought mere legend and horror story have begun to appear.
Then into town comes a band of adventurers. One amongst them looks to be a fiend from hell, another seems to be part man, part horrific reptilian beast - the type of monster mothers may have used to frighten children into good behavior while growing up, but now fully realized in a form that even gives adults a momentary shiver of apprehension.
Do the townspeople - frightened as they are by these recent, strange, and terrible occurrences - seek out the adventurers and request their aid? Or do they presume that these 'adventurers' are in fact members of the cult that has taken and likely slain their children, and no doubt seek far worse in the near future - perhaps now amongst them directly to scout out their weaknesses in preparation for take-over? Do they trust these adventurers - including the part-fiend and part-dragon amongst them - to deal with the evil cult and terrible monsters that they now believe to be plaguing them, or do they presume they are now in the presence of those (or [knowingly or unknowingly] agents of those) that have been terrorizing them and abducting their children - no doubt for foul and horrific evil rituals?
I don't know about you, but I expect pitchforks, fire, and ranged weaponry to be gathered as soon as the first townsman sees the adventurers coming and runs back to tell the rest of the town what is approaching them. I expect arrows, bullets (slings), and bolts to be hurled before any attempt at conversation is possible. If the party manages to get into town before a mob can gather, I expect a mob to form around them, an angry and vengeful mob - all because of how two of the party appear so inhuman and monstrous.
Be honest. Presume you are living in the dark ages in Europe, some mostly isolated village, seeped in superstitious beliefs in magic, fey, monsters, dragons, etc. Then something that looks like the Predator boldly walks (or rides) into town. Even presuming he comes with a group of three to five fully human mercenaries, how likely are you to not join any mob that forms to deal with such a potential menace? How likely are you to listen to their pleas that the fiendish appearing one is not evil? Especially if strange things have been happening recently?
Heck, in a PoL setting *any* outsider - even human ones - are going to be treated with caution if not hostility, at least at first. After all, even a nice (and human) face could hide an evil priest, a savage mercenary, a malign con-artist, a fiend or fey in disguise, etc. How much worse will they view faces so utterly monstrous in such a setting?