Up to four locations now, the Press reports they’re all within a 1/2 mile radius of each other.
I’ve only ever been to the location in the Viet Hoa Center right on the Beltway @ Beechnut, the easiest one for me to access. I happened to spot the third one recently - hadn’t known that one existed - and thought it was very close to the others. I’ve never been to the original which is smaller and known for lines.
The breads are fun, and good. My favorite is the red bean bun. I usually don’t get there until after noon and there isn’t as much selection as there would be in the morning.