Forget your friend and forget the coach. Just follow your heart. Play the sport for the love of the game even if its not tennis!
By the way, there's a kid out of Seattle that is a great tennis player but an even better runner. If you like them both, why not compete in both?
If you live in a strong section and continue to excel, you can find a college. Don't worry about chasing these national tournaments for a college scholarship. IMHO it's not necessary if you live in a strong section and have success against other players.
Good luck kid. You'll do the right thing.