Preheat your oven to 400°F (200°C). Carefully slice the spaghetti squash in half lengthwise, scoop out the seeds, and place the halves cut side down on a foil-lined baking sheet. Roast for 25-30 minutes, or until the flesh is fork-tender and easily shreds into strands.

While the squash is roasting, combine the sour cream, cream cheese, cheddar cheese, Monterey Jack, minced garlic, and salt in a large mixing bowl. Blend until smooth and creamy. Gently fold in the chopped bacon, diced jalapeños, and green onions.

Once the roasted spaghetti squash has cooled slightly, use a fork to scrape out the flesh, creating spaghetti-like strands. Add these strands to the creamy mixture and fold together until evenly combined.

Spoon the creamy mixture back into the halved spaghetti squash shells, pressing down gently to pack it in. Top with reserved bacon and green onions. Return to the oven and bake for an additional 5-6 minutes, until edges are bubbling and golden brown.

Once baked, allow to cool for a few minutes before serving warm.