I've now had two mango milk tapioca pearl tea drinks at Sweetheart Cafe at 9th and Harrison in Oakland, and it's confirmed - they're the best in the East Bay! The mango was real (always preferred over powdered mango), the tapioca pearls still warm and nicely soft (not jaw-breakingly chewy like some are), and the whole thing frothy and perfectly mixed. Yes, it was $3.50, which is double what I paid for my actual lunch of take out dim sum a couple blocks away. But it was completely worth it. Now I just have to get myself to try other flavors...like durian! (Sweetheart offers at least 100 different varieties.)
Here's a link to the Pearl Tea Review's report on Sweetheart, which also has a location in Milpitas and one on Durant in Berkeley.