Thats a mature male Brachypelma vagans, commonly known as a Mexican Red Rump. I see the males every year when we're on AC. The males wander around once they are mature looking for females to mate with while the females usually don't stray far from their burrow and are much less likely to be seen. You can tell it's a male by the small hooks or spurs that are under the two front legs. The males use these to engage the fangs of the females during mating so they can complete their business before the female makes a meal of them.
There are about eight species of tarantula in Belize and Brachypelma vagans are found pretty much country wide. I have yet to find any other species on AC although I keep looking.
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Cleverly disguised as a responsible adult.