Anyone 21 or over with a valid photo ID. That's the whole rule, and it applies to everybody who walks through the door — not just the person paying. If your friend is coming in to look around, they need their ID too.
Nobody under 21 can come into a licensed adult-use sales area in New Mexico. That includes teenagers, children, and babies. It isn't a house preference we could be talked out of; it's a condition of the licence, and it's the reason the drive-thru and curbside exist — if there's someone under 21 in the car, that's exactly what the window is for.
The same goes for buying on someone else's behalf. Purchasing for anyone under 21 is illegal, and it is the fastest way for a shop to lose its licence. Please don't put us in that position.