I know, I know, carnitas aren't quick. You need to roast the pork forever.
But not if you've got a Northgate Market near you. And if you live in southern CA, you probably do!
MIL came home with two large chunks of roasted pork, tub of "salsa mexicana", and a pack of guaraches (thick slipper-shaped corn tortillas). I shredded the pork and skillet-fried it without adding any fat, until it got crispy. At the same time, I placed the guaraches directly over a low gas flame to heat them through and get a little crispiness. Then pile some carnitas on a guarache, add some lettuce (or green onion or cilantro if you have it), a squeeze of lime, and a dollop of salsa.
Alternatively, spread some salsa on your guarache, and distribute the carnitas on top, then bake until slightly dried out and a little crispy. Hubby says that guaraches are normally spread with a chile paste (much thicker than the salsa we had) and baked until the chile dries out, then topped with some sort of protein, some avocado, cilantro and lime. Sounds amazing, but I didn't feel like making chile paste, and didn't have any cilantro or lime. So you get what you get, and you don't make a fuss.
Quick, easy, not too terribly bad for you, and totally delicious.