Generally I unclip my left foot due to the crown of the road. I am fully ambidextrous on this topic though and will sometimes unclip my right foot if there's a curb or the road is really flat. This assumes I'm not getting off the bike, and am leaving the other foot clipped in.

If we want to talk about dismounting or remounting, swinging a leg over the saddle, for me it's non-drive-side only. I find it very difficult to get on a bike from the drive side. I have no order or preference on clipping in, but swinging my left leg over the saddle seems nearly impossible. I blame years of cyclocross and practicing dismounts/remounts on one side only.