Most men won't object if a woman sits on, however, they are pretty hositle to each other about drafting without asking.

I was TERRIFIED when I was taught to draft, I can't imagine just doing it for the first time. Now it's second nature, but the first 10 miles I was scared spitless, my now coach rode next to me the whole time saying "closer, closer, bend your elbows, closer, that's it, gear up, good, closer."