Geographically speaking, up is north and down is south (if that's wrong, my entire question is dumb). My friends keep saying they are doing something "down here" when they are actually talking about the neighborhood they live in, which is in fact 9 miles due north of me. They complain when I comment on the fact that they're wrong (I don't point it out that often, but sometimes it irritates me). Can someone just confirm for me that they are wrong and I am right? Thank you.
"Down South", "Up North", "Way Down upon the Swanee River", Down in Florida, up in The Yukon, down in Antarctica", etc. etc.
The precedent is there, and you are correct with regard to direction. However, "down home" is also very prevalent, and when referring to where one is (from an idiom meaning simple, comfortable, old fashioned but with good connotations).
Down here is very common (when it is one's home), perhaps due to other absorbed idiomatic phrases.
For very long distances cardinal points are the obvious points of reference, where down is south and up is north.
But for relatively short distances it's rather features of the natural (or man-made) environment that decides what is up and down, eg. if you live uphill/downhill from the other person, or upriver/downriver from that person regardless if the river flows north or south.