Put 2 jalapenos into a small bowl and top with 1/2 cup plus 2 tablespoons tequila. Cover and refrigerate for a day. Pour the spicy tequila into a pitcher and add 1/2 cup plus 2 tablespoons chilled lime juice, the orange liqueur, and the guava juice, and refrigerate again until chilled. Put salt into a small plate and use lime wedge to moisten the rims of margarita glasses. Halve, remove the seeds and thinly slice the third jalapeno. Garnish each glass with 1 slice. Pour the chilled margarita mixture into the glasses. Serve.