Ok, I totally agree with you that Dean is using code so as not to alert the muggle. But the fact that he has to say it twice, very deliberately, before Sam gets it sort of suggests that there's a nominal 'home' from which Dad occasionally goes missing for reasons unrelated to hunting.

Also, John makes it pretty clear that the reason he was so angry about Sam leaving (apart from being proud and stubborn) was that he was worried because he wouldn't be able to protect him anymore (you were talking about this in an earlier post). Given that, it makes sense to me that he'd 'settle' (if you could call it that) near-by so that he could keep an eye on things. Especially if, as you say, he suspects Sam is important to the Ceiling Demon. From that perspective, setting-up base near Sam makes sense not only as a protective Daddy thing to do, but also as a my-life's-purpose-is-to-find-the-Demon sort of thing to do.

But yeah, not actually in the show, just the impression I got.