Robert Silverberg's "The Day the Monsters Broke Loose" isn't anything great, but it's the best story in the magazine. It's about just what the title says it is.
"Beasts of Nightmare Horror" by Richard F. Watson is also about just exactly what it says it is, and it's sort of a Forbidden Planet/alien-invasion/frontier/WWII story. It's the issue's "novelette."
"Mating Instinct" by Lloyd Biggle, Jr., isn't part of the monster motif. It's story about an alien invasion that fails. Attitudes have changed a lot since the '50s.
Here's a bit from "The Enormous Diamond" by Bill Wesley: "The bitter odor of Venerian hashinrut, the twang of loose-stringed Capellan guitars, the appreciative grunts of the huge Sirians as they feasted their tiny swollen eyes on the smooth-skinned Venerian belly dancers -- all this he had seen before." And all this you've read before in the SF digests if not the crime digests (in different words, of course). I'll be George Lucas could say the same. I love it.