Hi, Gordana
"Is it better to promote SFI to friends and family ... or to strangers?
I think all of better, we can promote SFI to friends, family, and strangers.
If you look like me, can't talk with strangers, so we can share with our friends and family. Maybe they will laugh or didn't believe, but it's ok. We can talk to them with a simple word.
But you can promote to strangers with making video or send e-card, that the simple way.
Hope this help!