Chrysostomos,
What I have seen is that it depends on what languages the priest speaks and what background the people generally have.
We have one priest who "only" speaks Russian, Georgian, and Greek - he has had services in Greek and also in Russian.
There is another priest who was formerly Roman Catholic - he has all the changable parts of the services in English and all the typical parts in Greek.
There are all English services at our Cathedral as well as all Greek.
In fact, one of our bishops doesn't speak much Greek at all.
So it just depends, but as a whole (not just my synod), I would guess generally, you will find 75% Greek, 25% other.
I am just speaking for the Greeks here, I'm not sure about the Russians. Hope this helps.