PHILADELPHIA—After a few hours, the abundance of Cyrillic signs begins to blend together with the smells of eastern European delicacies: cabbage samsas, honey-sweetened poppyseed pinwheels, and lamb pilaf. Inside the well-trafficked supermarkets—the main draws of the low-slung strip malls that define this part of northeast Philadelphia—you hear boisterous conversations in Uzbek or Russian, and more staccato versions in English.