Garlic is a great companion plant, it accumulates sulfur, a naturally occurring fungicide which will help in the garden with disease prevention. Sulfur is also good for lowering the soil pH, normally you would add sulfur or ammonium sulfate to make the soil more acidic for these berries so Garlic grown with blueberries is helpful in this respect.
The drawback to this scenario is that garlic does best in a soil pH of 5.5 to 7.5, while blueberries prefer a pH of 4.8 - 5.5. So they are not 100% compatible, but they are close enough where they can be successfully inter-cropped. The garlic will not do as well as it could, but it will still serve a function of helping to maintain the pH for the blueberries, suppress pest and disease issues while yielding an edible crop.
Garlic also has pest suppression properties. It discourages aphids, flea beetle, Japanese beetle, fungus gnats, codling moths, cabbage loopers, ants, snails and spider mites. There is also some proof that it deters mammalian herbivores such as rabbits and deer.