For those that have PCSd overseas have you taken advantage of JKO language classes or anything else prior to assignment?

Sounds like a Good Program/System. In my case was before it existed and not necessary, I was stationed at Naval Communications Unit London, UK (I think my English skills are OK and Diego Garcia British Indian Ocean Territory English again although they do spell tire, tyre) I did travel to Germany but I had German Border Guard as a Minder and He Came in Real Handy.

The Army transitioned from Rosetta to HeadStart a few years ago. I've used both. I didn't like Headstart much. Rosetta and DuoLingo would be a great combo.

Regardless of what resource is utilized, I feel that it is important, if not professionally responsible, to understand, appreciate, and inculcate the culture of the region in which we will operate. Understanding the language, and communication preferences, goes a long way.
My Family and I are going through the same process now. I found JKO to be less than helpful and difficult to navigate. So, I pulled the trigger on big yellow box (Rosetta Stone). It was certainly worth the price tag.