The Sterling location has 3 monthly specials listed for September.
I just finished the Pla Goong from the specials menu, a shrimp and lemongrass salad. It is full of torn lettuce (possibly Romaine), red onion, scallions, lemongrass, and shrimp, all in a nicely balanced citrus and lemongrass sauce with just a bit of heat. I'm hoping this dish makes it onto the regular or secret Thai menu. It was about the right size for a single dish lunch.
This dish could ALMOST make me forget how wonderful their far less healthy fried pork dishes are.
I can't speak to the Fairfax location at the intersection of 29 and 50. Has anyone been there lately?