In a small bowl, whisk together the lime juice, zest, and salt. Add the oil slowly and whisk until incorporated. Set aside. (You can make the dressing up to 1 day ahead. Cover and refrigerate. Bring to room temperature before using.)
Drain the pre-cut watermelon, if using.
To assemble: Toss the watermelon with the cheese. Add the dressing and herbs. Taste and depending on the saltiness of the cheese, add salt a little at a time to bring out the full flavors of the salad. Garnish with mint sprigs and serve right away.