When I'm on a group ride in roadie mode, pretty much everything and everybody on the street registers just as an obstacle to watch out for. If there is a group of roadies behind you heading in the same direction, you might hear "rider up!" before they overtake you (assuming you're going slower). That's as much of an acknowledgment as you can expect but sometimes I'll greet other riders as we go by.

I'm usually focused on the rider in front of me or if I'm pulling, I'm looking out for obstacles and trying to maintain a good pace.

It doesn't matter that you're not wearing lycra, although if there were several of you wearing a different type of kit, it might trigger an "attack".

There's really no offense intended.