I had a reply written, but then teh internetz went kaput and I lost it all. So.
Basically, even if you get a horizontal flag, if you're going to hang it vertically, you should flip it so the Union's at the top left. But, while the Flag Code is technically federal law, it's not legally binding thanks to the First Amendment. So, really, you can hang it any way you want, but there is a right way to do it.