OK, check out this situation.
I'm prior service Marine infantry. I joined the Guard last May as a Medic with an MP unit. My PMOS is 11B- infantry until I go to Medic school. But that won't be for a few months or more. I'm listed as a medic on our roster and am acting the part because I am a civilian EMT but I'm not MOS Q'd yet.
This Veterans Day I have an event to go to at the Capitol that I need to wear my class A uniform.
Do I go with the medical caduceus (the staff and snakes) insignia or the Infantry crossed rifles on my lapel. If I wear the Infantry do I wear the Infantry cord becuase the regs state I can if it is my PMOS but I'm not in an Infantry unit.
No one at my unit has a clue.

I would wear what I was qualified to wear. Since you are not MOS qualified as a medic yet I would not wear it. SO go for the Infantry rifles and blue cord. Don't forget the blue background for the US and crossed rifles.

Tiz what I would do anyway.