Main Street bakery opens when they open up Main Street for guests at rope drop. There's basically always a line, though it is shorter if you arrive in that first burst of folks through the gate. However, how much are you trying to accomplish at rope drop? I just ask b/c time spent in that line at Starbucks will place you further back in the crowds which immediately start lining up at the "spokes" of the hub. If you can schedule enough time to grab tea at your resort, that is probably the better option if you want to fully take advantage of the rope drop time period for attractions.