How do I get into rodeo?

For about 3 years, I've wanted to do steer riding, but my mom won't let me, because it's a 'boys sport'. In a few weeks, theres going to be cow riding at a rodeo my sisters boyfriend will be in, and his bull riding friends said they'd help me. But, my mom said 'maybe,' which means 'no'. How do I convince my parents to let me do this? I know the risks, and I'm generally a responsible person, but this is something I really want to do.