Originally Posted by Travellin' Fool
In my experience even flying through the southwest airports the only time you see "la migra" is when you go through customs. Domestic flights shouldn't be an issue at all.
In LRD, there are agents standing at a podium after security asking all passengers if they are US citizens, regardless of where their flight is going. I'm not sure if they do this at any other border airports, but they've done this at LRD since before 9/11.