I don't see any disadvantage and it will get you a head start on lowering pH. Aren't you in a pretty warm area? If so your bacteria might have another two months of decent soil temperatures. I just added some to pots in my greenhouse. Don't really expect to see much until next yr but it will be a start.

It is my understanding that elemental sulfur takes up to six months to lower the pH. I would add it now and allow it to break down before the berries bloom. Additionally, I would add pine mulch to the soil ( I use up to 40% pine bark mulch and/or ground pine needles in my planting beds). This helps keep the pH regulated at a significantly low enough level (I shoot for 5.5 to 6.0). Last year I worked hard at maintain a pH of 5.8 and had my best yield of the tastiest blueberries I have ever eaten. They were so good, I didn't give any away.