You're going to run into problems with this, because each MySite in
and of itself is its own site  collection independent of other
collections. That and I'm guessing that your MySite installation
probably even runs on its own port independent of other site
collections, since that's the way it's typically configured. I'll let
the gurus on the list provide information if they think there's a
workaround, but since they're essentially two very different service
types, I'm not sure I see how you'd be able to pass this information
around.

Sorry to be so late answering on this.

Found the question looking for something else.

Here is what I would try:

On two separate applications create  one MySite host per application, one
using the English template, one using the French template.

List both of them as Trusted MySite hosts.

Target your users (via domain groups as an audience) to the appropriate
MySite host.

Surely you have groups that identify the users by language.

MySites created  on a MySite host should match the language  of the host
unless you check the box to allow users to select a language which is
not what you want to do.