All healers are viable in PvP currently. Play what you think will be fun. If you're going for glad, which it doesn't sound like you are, research it on:
http://www.worldofwargraphs.com/stat...0-0-0-0-0.html
I have all healers other than Shaman, I just hate their playstyle. Druid and Monks are fun because of mobility. Disc and HPal are fun because of their "tanky" feel. I have not tried HPriest but I know they are considered the better Priest healer by many due to, basically, Guardian Spirit and Chastise. Can't freaking wait for Chastise to be useless in WoD. Sorry, I digressed. But, until 2k and probably even 2.2k any healer is viable, although as stated with varying comps as options.
Have fun and welcome to healing: it can be annoying, learning to "juke" interrupts and silences but it's a very fun aspect of the game!