wanting to travel down baja to San Quentin for clamming.

CAVEAT: The marinas will smile if you have clams enough to for clam bake or caldo de siete mares and not piles of them. Simply smile, shake hands and wish them buenas dias o tardes. Get caught with a gunnysack and things change for the worse.

But Turtle-Toad is correct Mexican authorities are touchy especially of foreigners seemingly sneering at Mexican law. I would have a fishing license even though it entitles a person to zero mariscos.