The first 2 google hits if I search for "LG 49LJ550M Default input source" (without quotes, just your subject line) are your posts here and on avsforum.com.
The third hit is a youtube video showing how to do in in hotel mode: https://www.youtube.com/watch?v=g5V1yFHB20M
Don't you love google (youtube is google also)?
To be fair: on BIng that video was the top hit. It didn't (yet?) show your two posts.
I only have one question which has been killing me. I have a LG 49LJ550M tv and can not figure out for the life of me how to change the power on default input source. It is currently on live tv and I don't have cable so I get that lovely static sound every single time I turn on the TV. I have other input sources hooked up also. Can anyone help please!!!