Maybe it's just that I like it so much and it could fit in this situation, lol.
It will be sun-hardy once established (seedlings may need some protection until they're about a foot or so, give it a few weeks) and looks like Red Japanese Maple. With the addition of the red Hib. flowers of course. The stuff grows like mad, a seedling grew to 4' in 1.5 months for me. Once it gets that tall, you can top it off and keep trimming it so that it will fill out and become more of a solid hedge.

Bamboo is fast. So is Variegated Hau. Duranta is fairly quick and bears those beautiful blue flowers and golden berries at the same time. Even a row of bananas might work. A'alii is moderately fast and a native. Since you mention trees, Glircidia might be another option.

Keep in mind that how fast the hedge grows is usually a pretty good indicator of how much maintenance will be required to keep it in bounds later. Don't ask me how i know ; )