Put the sweetened condensed milk, half-and-half, lime juice, lime zest, and salt in a bowl and whisk until thoroughly combined.
If using conventional molds, divide the mixture among the molds, snap on the lid, and freeze until solid, about 5 hours. If using glasses or other unconventional molds, freeze until the pops are beginning to set (1 1/2 to 2 hours), then insert the sticks and freeze until solid, 4 to 5 hours. If using an instant ice pop maker, follow the manufacturer's instructions.
Spread the graham cracker pieces on a large plate. Unmold the paletas and press each side into the graham crackers, coating completely.
Photograph by Ed Anderson (c) 2011
Recipe courtesy of Paletas: Authentic Recipes for Mexican Ice Pops, Shaved Ice, & Aguas Frescas by Fany Gerson.