Should I sing and follow my dream?

I recently received an email about America's Got Talent coming to my state for additions.I have NEVER sang in front of someone in my "singing" voice. If I do sing in front of people its just silly and I play around with it. I was told to always follow my dreams and it would be my dream to be able to sing in front of thousands of people and for them to love me! It's not about money to me. Yes who wouldn't' want to be rich and famous? But if I was a famous singer I would want to help people. Maybe with homeless people? Or help abused animals find loving homes? Or even volunteer to build homes for people who lost them in disasters. Overall my question is, should I just go for it? If I was to do something like this I don't know if I would want to tell people. I hate when someone has such high expectations for me about something and then I don't accomplish them. Should I go for it anyways? I'm afraid that I will get too nervous, like I said... I've never sang in front of anyone before. I feel like I have a good voice, but I'm sure a lot of people think the same thing and they just don't have it. I don't know if I have it.