Roses, gerberas, or other bright non-marigold flowers are safe defaults for a casual gift. Save marigolds for their intended season and context around Día de los Muertos (late October–early November), when they’re expected and meaningful rather than out of place.
As elsewhere, odd numbers of stems are generally the safer choice for a gift bouquet, and white blooms are worth skipping too, they’re closely tied to funerals.
If you want a flower with local meaning that isn’t funeral-associated, the dahlia is Mexico’s national flower and reads as a thoughtful, safe choice for almost any occasion.