Anyone can write diversity. It won't be right for everyone, but you'll get it right for some. Boys can write girls and girls can write boys. Avoid clichés, but realize there aren't single types of people no matter race, gender, or sexuality. "Cliché" is ambiguous - there will always be someone who says you're wrong. No matter, you'll get it write for someone (see what I did there?), and that someone will feel a little more right in the world. Try.