Virgin mobile will offer the iPhone 5 in all service areas once apple sells them factory unlocked. It could be months before apple releases an unlocked version, so if you want an iPhone right now, I suggest going with a contract carrier
Did a Search and One poster wrote that the iPhone 4s was sold on Oct 14th 2011 and Apple unlocked it on Nov 11th, 2011. Might be next month for the iPhone 5. Not 100%.
I think it won't be available for awhile (maybe mid-2013) since Sprint owns VM and they want to draw people into postpaid plans as much as they can before they start selling it with VM prepaid plans. Also you can't just BYOD to VM.