"Is 20+mph on flats easy for you guys? I mean I can probably sutain 20mph with some tailwind for maybe 20-30 mins but after that I am pretty much exhausted"

Piece of cake if you add in one day of 42-45mph sprints and one day of 27-35mph intervals per week. After that, 20mph+ on the flats is pffftt... CRAP!!!

As for the interactions with other cyclist, I'm usually friendly and at least say, "Hi, how's it going"? If they don't respond, I just move on. Some people accuse me of being a ditzy, bubbly blonde on the inside, not sure if I should take that as a compliment or an insult..