Your motivation's good, and I think most people will probably get that. 🙂 I'm far from a social person, but even I appreciate good trail etiquette and just nice outdoorsy community feelings, if that makes sense.
Sometimes I get people blithely assuming I'm much less experienced than they are, and that's somewhere between amusing and annoying usually. If you're gonna start giving unsolicited advice, maybe go with a quick "Been up here before?" or such first.
Hiking nearer to Quebec, "Bonjour" often seems appropriate, though then I immediately wonder if my accent's as good as it was in high school. Beyond that, "Good morning," "Good afternoon," and "Have a good one!" are my boring usual greetings.