Even after passing medicals you can be cut...happened a lot.
CartAttack - I personally wouldn't say anything until you have the job offered. As usually GS won't be immediately.
Depends on the job though you have now. I know on my past job they would have been all happy for me to go for this either way.
But if it's a job/manager that might not be so supportive, I personally would wait till I have a job offer.
Given the nature of the industry, wait times and culling.