For the Ancho-Arbol Syrup, mix all ingredients in small saucepan. Bring to boil. Reduce heat to medium-low; simmer 5 minutes. Remove from heat. Let stand 2 hours. Strain through double layer of cheesecloth or coffee filters into pitcher. Cover and refrigerate until well chilled.
Mix sea salt and ancho chile pepper on small plate. Cut 1 of the limes into 8 wedges. Wet outside rims of 6 short beverage glasses with 2 of the lime wedges. Dip glasses into sea salt mixture to coat. Fill glasses with ice.
Juice remaining 2 limes. Add to Ancho-Arbol Syrup in pitcher. Stir in grapefruit juice, tequila and club soda. Pour into glasses. Garnish with remaining lime wedges.