If the curve is in pitches you throw, I'd do two things, first I would listen to my coach and work on learning a change of some sort. I say this for two reasons, !st and foremost, he's your coach and if you want to play, you should do the things he thinks important for your entire team in order to win and stay healthy. 2nd a change has little arm impact when thrown right. So you aren't being asked to hurt yourself, you are being asked to grow as a pitcher (Consider yourself a lucky guy because some kids don't have that benefit), which makes it win win for you if you follow his wishes.
After I've shown that I am on board with his wishes and working towards a common goal, I'm still going to continue to work on the mechanics of my curve, just as part of my bullpen or side work. No particular need to completely forget about the pitch and he may allow you to show it a some future point.
I generally agree with him though, the change will allow you to work location and change of speeds with your fastball, so if you work hard and make a comittment you'll be a much better, some would say much healthier (sp?) pitcher, with a very good group of pitches and dependant on none.
Smells like a great year for Mr. BDrogon04!!!!!