I prefer right foot forward heavily, too, especially when my hand/hands aren't on the bars - but if I'm using my hands I can trackstand in all direcitons, just I very rarely go left/left due to my own comfort.

I usually try for the roll to the green game, but there's often enough those times where I hit the light for the full cycle (har HAR) so I trackstand for those usually.

I trackstand most of the time whenever waiting, but don't feel any obligation to do/not do them. Just whenever I feel like it.