Slowly, but surely, Silver Spring is turning in to a bicycling city. I'm am, or was, a commuter during the summer, from the Langley Park neighborhood to downtown D.C. and back, almost all of it on the street and what difficulties I've experienced were mostly self induced. The terrain is relatively gentle hills, although the downtown area is flat. Plenty of multi-use trails and bike lanes. On Sundays they close the Sligo Creek Road to cars. That's about five and a half miles of flat road with good pavement if you want to ride at speed. I can't speak for north of the city, but D.C. has gotten to be very bicycle friendly. From what I've been told, Virginia side is hillier than Maryland. There may be a couple of very hot days in the summer when bicycling can be dangerous. Winters are hit or miss. Up until January we were experiencing fifties during the day and thirties at night. Right now it's hovering around zero degrees with snow and rain expected.

Look up the WashCycle blog. The author keeps a close watch on bicycling issues in the DMV.