Hi there Jon, and welcome.
Just a few words on the subject of handedness if I may (hoping it doesn't sound too preachy as it's not meant to)...
First up, it's not an either/or. Most people can do things to a certain level with their 'wrong' hand at need. Total one-handedness is actually rare. You probably know this already, but all the same...
That said, most people have a preference one way over the other. It can vary very widely as Douglas has indicated above, with people routinely doing different tasks with different hands being fairly common. Again though, proper ambidexterity (the ability to do all things equally well with either hand) is pretty rare.
As has been said above, try both ways and let that be your guide. If there doesn't seem to be much difference then you might as well go Righty. If it feels very different then you'll know fairly quickly even as a beginner. (You could still go Righty in this latter situation of course, but you need to be prepared for the likelihood that it'll be hard work - as in 'harder than if you'd gone Lefty'.)
One more thing: there are couple of myths about handedness on a guitar that you need to be aware of:
1. "It's all a bit strange at first so you might as well play Righty." In my years as a guitar tutor with the RGT I once had a protracted and heated argument with - of all people - a senior and well-respected member of the Registry over this through the pages of our professional journal. Yes it is all a bit strange at first, but that doesn't necessarily make it an equal challenge.
2. "Left handed players have a stronger left hand, and since the fretting hand does most of the work you should really be playing Righty anyway." I've heard this one on a number of musicians' forums (including, sad to say, Guitatchat's sister site, Basschat). In the first place, it isn't the case that the fretting hand does all the hard work. All the fretting fingers need to do is be in the right place at the right time: the subtleties and nuances of note production are carried out by the strong hand. In the second place, even if it were true, then by that logic all right-handed players should be playing Lefty!
Hope this helps.
ETA: In case this seems a little OTT given what you've said up top, around 90% of the population is predominantly right-handed, so the fact that you've mentioned left-handedness at all indicates that it's an unusual thing to be considering. Hence the speil.