Any idea what this is? Seek says it's in the genus Erythroxylum, but it can't get any more specific than that.

Unfortunately, the Caribbean is a large and very diverse region which is underrepresented among the community here and probably in training data for plant apps as well.

If you can come back when it flowers or fruits that would make it easier. Or sharing a more specific location.

Erythroxylon rotundifolium, urbanii, carthagenense, havanense, and especially brevipes all look superficially similar but I’m not familiar with this genus. They all have glaucous leaf undersides so consider adding a photo of that feature to help verify.

If you are really committed to IDing the plant, you may need someone with local expertise.