Squeeze the water out of the spinach, and place the spinach into a mixing bowl. Stir in the onion, garlic, vegetables, sour cream, mayonnaise, and cumin. Season with salt and pepper. Let the dip stand at room temp for 1/2 hour for the flavors to mix, and stir again before serving. This dip keeps well in the fridge, covered, for up to 1 week.