I agree with BigRedX. There's sod all left handed instruments out there, so may as well try to play righty first!
I'm left handed for writing, but right handed for lots of other things. You need two hands to play bass, so the whole left/right handed thing doesn't make much sense anyway. You need more dexterity in your fretting hand anyway, so I don't know why more right handed people don't play lefty basses!