Preheat oven to 425°F. Coat a baking sheet with cooking spray.
Place tortillas on prepared pan; bake until crisp, about 6 to 8 minutes. Meanwhile, coat a large nonstick skillet with cooking spray; heat over medium-high heat. Add garlic, cumin and salt.
Next, in a bowl, mash beans and salsa with a fork until well-blended and most of the beans are mashed; stir in 1/4 cup cilantro.
To assemble pizzas, spread 1/4 bean mixture over each tortilla (slightly less than 1/4 cup); sprinkle each with 1 tablespoon cheese. Bake until cheese melts and topping is hot, about 3 minutes. (Broil pizzas to brown cheese even more, if desired.)
Meanwhile, in a medium bowl, toss together tomato, avocado, remaining 1/4 cup cilantro and lime juice.
Remove pizzas from oven and top each with 2 teaspoons reduced-fat sour cream and about 1/4 cup avocado mixture. Yields 1 pizza per serving.