Would love to, Eric! (Depending on timing, of course...)
(And, I think I owe you an email...)
A nice ride, staying mostly on local paths is: (i) start south of the Anacostia, along the Anacostia Riverwalk trail; head northeast along the trail to Bladensburg; (ii) when you hit the fork where you can take either the Northwest Branch or the Northeast Branch, go left and take the Northwest Branch Trail; (iii) turn left onto the Sligo Creek Trail; keep following that until the trail ends (or, rather, becomes more of a pure walking path), and then just take Sligo Creek Parkway north; (iv) when Sligo Creek hits Forest Glen Rd, take Forest Glen left (west) and then find your way down to Forsythe Ave/Jones Mill Rd.
At that point you can decide if you'd like to head north-ish on Beach Drive for a few miles, ending up at Garrett Park, which is the local turnaround. Or you can go south on Jones Mill, which will lead to the southern section of Beach Drive. That section of Beach Drive is closed off to cars.
Once you've gone down Beach Drive, there are multiple city-street-based ways to get back to the Anacostia Riverwalk trail.
Will do up a Google Maps thing so you can see what that looks like...
Cheers!
Liz Sherwood
Washington, DC