Creating robot programs can be done online (with the teach pendant) or offline (using Fanuc's s/w on a PC).
The robot's serial port could be used in a very basic fashion where the robot program just periodically sends out process information (such as the value of an analog input) and a PC collects it.
I've yet to design a robot cell without having a cell PLC that acts as a master and the robot acts as a slave. The PLC is connected to the robot using a fieldbus connection (profibus, profinet, device-net, ethernet/ip, or ethernet-global-data) and any process information was given to the PLC via the fieldbus connection because its often easier to get information out of a PLC (when connected to a PC).
So, if you don't have that architecture, I would imagine sending process information out the Robot's serial port is a method that could be used. However, I don't know of a way to program that in the robot without having the Karel programming option.
So, do you know what options your robot has and what the cell architecture is that it will be operating in? Host PLC? Or standalone?