MM3 it is!
Behold the delightful ambush drake: first monster of this new book. Its CR-to-HD ratio is somewhat concerning (5:7) but then again it's dragon type so perhaps that'll balance it out.
Ambush drakes are medium-sized, have bonuses to all physical stats and small penalties to intelligence and charisma (though they're still smarter than, say, ogres), and enjoy +6 natural armor. They have an above-average land speed and a slower, poor, fly speed (still useful for avoiding obstacles and such).
Furthermore, ambush drakes have a bite that deals dexterity damage (not bad at all), as well as two claws. They have a breath weapon that causes a Slow effect which lasts for 7 turns, giving them a decent debuff. Finally, they get the oddball Telepathic Link, which is largely useless if no other PCs are ambush drakes.
So what LA to give? Considering the pretty good RHD, the quite useable abilities, and the okay chassis, I feel like +0 can be justified here.