One thing experienced athletes possess is an inner confidence. They exude it, and it can be detected by others. A lack of such can also be felt by such persons. If you are new, a beginner, not confident, you project such.
When you are riding and keep telling yourself that you are a beginner, others around will feel the same about you. That's why you need to observe, practice a lot when you ride solo, and you will gain the confidence that only comes from time spent on the bike.
Then, when you feel like waving, you wave. It doesn't matter if they wave back; if they wave at you, you can wave, you can nod, or you can just look at them. You will know who you are, what you are capable of, have that inner calm, and that can't be taken away by someone else's reaction because it wasn't built on that.