However if your motivation for a masters was to hide out from harsh economies, I'd actually argue that you would be better off doing something non-PR. You have the undergrad journo thing anyhow, no one can take that away from you.
Your employability would be better aided by doing a Masters in a field unrelated but offering good new business opportunities for the PR firms, or for the PR departments of firms in [WHATEVER] industry. Comms grads are a dime a dozen. The PR firms are looking for people who understand healthcare, financial markets, IT. Pick something that you have at least a passing interest in, and that either common sense or economic data tells you that there is money in. Come out of that telling potential employers that your specialty is in one of these as well as communications, and suddenly you stand out from the other eleven CVs someone paid the aforementioned ten cents for. The reality of it is that the finance grads don't want to do comms - they all want to be in investment banking, and the comms grads spent too long reading about Gender Issues In Communications to learn anything that anyone would actually want to pay them for.
Social media came up above....and while I am absolutely not questioning its importance to my profession, I'm not sure that can really be studied...it changes so fast that by the time someone formulates a class on it, the reading list is already redundant. You will probably just know enough about it by growing up in and among it, and reading a few articles on it as you go, and giving The Meaning And Implications Of It All a good hard think. That said, if you can graduate right now with some piece of paper that says you know something about Social Media that All The Other Kids Don't Have, then you are golden as an employment prospect.