El Rey ruins at sunset is absolutely magical for photos. Most people skip this Mayan site because it's small, but that's exactly why it's perfect. The light hits those ancient stones around 6pm and you'll have the place almost to yourself.

For sunrise shots, walk down to Playa Delfines early - the elevated platform gives you that perfect view over the coastline. The lifeguard stations make great foreground elements too. Just bring bug spray because the mosquitos are real at dawn.