Basic registration is free and while it is a little busy to navigate, once you're logged in you can immediately decide whether the Garita Otay or Garita San Ysidro is the better way to leave Mexico. I just don't know how updated the info is.
I've found the webcam for entering Tijuana at San Ysidro helpfull; I can see if there's a backup.
There's lots of websites offering info. on the border wait entering the US but little on entering Mexico










