If someone who resides in Mexico and is a Mexican citizen wants to cross over to visit me and go shopping, what do they need?
They NEED their passport and a valid visa, Most get a B2 Crossing Border is a little more than waving your ID at the doorman. They do not have to let anyone pass. They NEED a reasonable plan for their time in the USA a reasonable method to pay their expenses and a reasonable reason to be leaving the US when their visit is over. Simple example . returning to work as you are on vacation from your job.