Whizbang, Dragon's Delve isn't (as presented on the site outside of the conversion notes) in the countryside outside of Ptolus - it isn't in Praemal at all. The default setting is 'the Fallen Duchy of Chordille," a loosely defined border region 'forgotten by the outside world.'
Much like how Ptolus aimed to keep players inside the city by not presenting anything exciting outside the walls, DungeonADay keeps players in the dungeon by not presenting adventures outside the area. (Although there have been a few side-treks into other local landmarks on the path between the dungeon and Brindenford). The environs are vague and fairly generic, and short of restocking missions in town, most attention should be focused on the dungeon.
Beyond Monte's advice, this makes integrating the dungeon into Ptolus even easier. The dungeon isn't too deeply tied to anything in the outside world, so it would be easy enough to file off the serial numbers and toss it into the Dungeon of Ptolus.