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. Cover and refrigerate until well chilled. (This makes enough syrup for 4 cocktails.)
For each cocktail, place 4 pieces of lime and 1/4 cup of the Ancho-Arbol Syrup in beverage glass. Muddle the lime with a muddler or wooden spoon to release the lime juice. Fill glass with ice. Add 1/4 cup each Cachaça and guava nectar; mix well. Repeat with remaining ingredients to make 4 cocktails.