The secret is now out about the little BBQ joint on Avenue B in old downtown Garland. Meshack’s Bar-B-Que Shack has gone from obscurity to stardom over the past year. Their chopped brisket sandwich, on the menu at a cool $2.75, may very well be the best BBQ bargain in the DFW area. You can also buy a pound of chopped beef for $7.00. Travis and Donna Mayes opened Meshack’s in May 2009. They had been in the business 15 years earlier and wanted to make another run at BBQ greatness. Donna said they prayed about it and decided to…