"Devils?" asks the Doctor, in surprise and Scottishness, ignoring Aziraphale's backpedaling completely. "Yeah, come to think of it, that would be your business, wouldn't it. I'll take it," he answers brightly, even as the owl volunteers a very decisive sounding, "No. We aren't." The Doctor makes a face as though imitating the owl sarcastically, except the owl hadn't done anything remotely like that. Still, it gets the point across.

"Lots of devils in New York, then?" It's a deceptively naive, touristy sounding question. "More than the occasional miracle can handle?" And whatever thwarting wiles refers to. Divine ecstasy, at least, is probably pretty useful if you're resourceful enough.