You'll love this.
To make the pork, combine all the ingredients in a resealable 1 gallon plastic bag and marinate for 30 minutes.
While pork is marinating, whisk together all the ingredients for the vinaigrette.
In a medium bowl, combine all the ingredients for the salsa. Gently fold in the vinaigrette. Chill.
Trim off the soft dark green end of the romaine. Cut off the root end and separate the leaves to create 4 inch long lettuce "shells." Rinse, dry, and chill the leaves.
Preheat the grill to medium. Discard the marinade. Grill the pork for 3 minutes on each side. Remove from heat, let rest 3 minutes, and roughly chop into 1/2 inch pieces.
Fill lettuce shells with the pork, top with the salsa, and devour!