Wet the rim of two rocks glass with the edge of a lime wedge, then dip in salt to rim the glasses.
Add watermelon juice, tequila, lime juice, and Trader Joe's Jalapeño Limeade to two glasses, then stir to combine. Fill glasses to the top with ice.
Alternatively you could add the ingredients into a shaker, fill halfway up with ice, then shake to chill.
Garnish with watermelon wedges and cocktail umbrellas if you're really feeling fancy!