I'd never heard of Mexican oregano, but a caller on our Your Day public radio gardening call-in show mentioned it. She said it was a great plant, and tasty, too, with a delightful sweetness.
Hmm. I meant to look it up, but didn't.
While cleaning up my office recently (I'm prone to stacks, piles, and unorganized folders of interesting things), I found a clipping about Mexican oregano (Lippia graveolens) from the Brooklyn Botanical Garden's Plants and Gardens News, which I receive as a member. (Their publications are wonderful).
It's easy to grow, liking heat, full sun, and fertile soil. It's not apparently hardy in the Piedmont, being hardy only to Zone 10, but we can apparently overwinter it inside on a south-facing windowsill. The author, Scott Appell, says it's easy to propagate, too, from tip-cuttings, another way to keep it going.
He mentions its culinary qualities, too, and suggests that many cooks prefer it to 'regular' oregano (Origanum spp.)
Lippia isn't even in the Mint family (Lamiaceae), but in the Verbena family (Verbenaceae), but must be chemical cousins in terms of their leaf compounds.
Definitely something to try!