Post one: In SAL you go from the plane to the next plane. There is only "security" when you go to the USA which is where they check your luggage for liquids as you enter the boarding area. SAL going to BOG , nothing. In BOG, never been but it would not surprise me due to anti-drug efforts at the least.

Post two: If all flights are the same day in SFO TACA or Avianca etc., will print all the passes at once. They did for me for years on one stop flights, no reason two stops would be any different.

Why would anyone suggest no carry-on? Cameras, medicines, emergency clothes you would be insane to leave at the hands of baggage handlers in all 4 countries. You will end up with a bag with clothes and a rock inside.

Post three: Yellow fever for Colombia or Chile, nope, unless you are coming from a YF country. And you are not. El Salvador is not a YF country and your stopover in BOG is zero risk.

You know you can do research yourself with Google and the CDC vs. waiting for what might be wrong advice on forums:

Here is from the CDC: http://wwwnc.cdc.gov/travel/yellowbo...bia#seldyfm707

Yellow Fever

Requirements: None
Recommendations:
Recommended for all travelers ≥9 months of age except as mentioned below.
Generally not recommended for travelers to the cities of Barranquilla, Cali, Cartagena, and Medellín (see Map 3-24).
Not recommended for travelers whose itineraries are limited to all areas >2,300 m in elevation,2 the department of San Andrčs y Providencia, and the capital city of Bogotá.