I've searched far and wide (well over a day's worth of searching) to see if there's a night bus from San Gil to Bogota. I need to know because of my flight. If I can depart from Bogota earlier, I can save a lot more money; hence the need for the night bus. Can someone PLEASE help me determine whether or not there is a night bus?
San Gil is on the way to Bucaramanga, so any bus in the route Bucaramanga <-> Bogotá may stop there. But of course in Colombia it is important to cross check in advance.
I found a company called Berlinas that has a line:
Recorrido (route, it indicates one way, but both are shown in the timetable):
Bogotá, Tunja, Barbosa, Socorro, San Gil, Piedecuesta, Bucaramanga.
As a side note, take a blanket for your trip: in the buses they normally have the air conditioner in a freezing temperature!
This is kinda tough... I'm pretty sure there are overnight buses, but San Gil is a small town so it's not going to show as a "destination" stop or "departure" point you can find when you search for fares. Likely you'll have to call the bus company and ask what routes would go near or pass by your San Gil.. and if they even pick up people there. Search online to see which bus company websites have fares between Bogota and larger cities to the north: like Bucaramanga, Cucuta, Valledupar, etc. Certain companies are only in certain regions.
Here's a good list I found: http://www.colombiainfo.org/en-us/transport/bus.aspx
I noticed Expreso Brasilia has routes from Bogota to the north coast, which might be your best bet. Be sure to explicitly ask the route/road a certain bus takes to make sure they can let you on at San Gil.
I've heard you can find cheaper fares at the bus terminal itself, and also probably get better info than anyone else here could give you. Does San Gil have any sort of bus terminal? Do buses stop at any gas stations or restaurants there? Is there any nearby city where buses stop? Bucaramanga maybe?
ps: I've traveled by bus from Bogota to Cali around late December and the overnight fares were all gone... I think people prefer them I guess as traveling by bus is pretty tiring during the day (at least it was for me... 12 hrs was close to unbearable!)