Hi Scott,
You can look online for more info about any of these South Miami poolrooms. I'm pretty sure they're all open at noon on the weekends. Listed in no particular order:
1- "New Wave Billiards" 1403 Southwest 107th Avenue Miami, FL 33174-2527 - (305) 220-4790
They've also got about a half dozen heated billiard tables. It is across the street from FIU, and is "Best for the college-aged crowd."
2- "Doral Billiards" 7800 Northwest 25th Street, Doral, FL 33122 (305) 592-8486
They've got a ton of Brunswick Metros and about a half dozen heated Chevillotte billard tables. Their crowd is a touch older than New Wave's. It is the "Best Sports Bar/Pool room."
3- "SharpShooters," 7200 Southwest 117th Avenue, Miami, FL - (305) 596-0588 They probably have the best tables overall (Gold Crowns), and is the first one I'd consider a "pool room" where you're liable to find some action. They've got great specials from noon til 5, and another happy hour special from 5-8.