For the chicken, in a small bowl, whisk together the Dijon mustard, Worcestershire, brown sugar, salt and pepper.
Place the chicken in a gallon-size ziploc bag or shallow dish. Coat the chicken with the marinade mixture; there isn't a ton of marinade, a thin coating is fine. Refrigerate for at least 30 minutes (or up to 24 hours).
In skillet set over medium heat, cook the bacon until crisp. With a slotted spoon, remove the bacon to a paper-towel lined plate to drain the grease. Set aside.
For the pico de gallo, in a medium bowl, combine the tomatoes, onion, cilantro, garlic, jalapeño, and lime juice. Drizzle with a teaspoon or so of olive oil. Season with salt and pepper (important!). Refrigerate until ready to serve.
Preheat a grill pan or outdoor grill to medium-high. I use a pellet grill set to 375 degrees F.
Cook the chicken for 4 to 5 minutes per side until an instant-read thermometer registers 165 degrees F at the thickest part.
Without removing the chicken from the grill pan/grill, top each chicken breast with shredded cheese and bacon - the amounts don't have to be exact, just divide evenly on the chicken.
Cover the grill or grill pan and heat until the cheese melts, 1 to 2 minutes.
Serve the chicken warm with the pico de gallo spooned on top or on the side. Prepare to be wowed - so delicious!
