Question:  There are multiple gpus on our nodes.  How can I see which gpu is being used by a job?

Answer:  Torque reports the gpu that is associated with a job in the output of 'qstat -f'.  There is a field in the output that will look something like this:
exec_gpus = node01-gpu/0

You can't see which gpus are in use by looking at information about the node, but you can use 'pbsnodes' to get a list of jobs to check that are running on a particular node.