Being both a Consultant to Startups and an Educator to young people like yourself, I commend you first on getting international experiences of any kind. And it's great you have a good business idea!

Here's the beauty of applying to those companies - you can always say no or not pursue the job. And if you're not hired, that's the end of that anyway! Better to have an offer first before you think of this as a 'choice'.

As for someone working on your idea - odds are someone already is even if not publicly known. Let's go with that assumption. Remember that being first to market isn't important anymore (remember Ask Jeeves? Google it.)

Short answer: apply for the job(s) and simultaneously try to put a team and execution plan. See which opportunity takes root. Talk with me more, as I love working with students and young grads!

Best of luck,
Arjun