The "DC Advantage" for Endurance Athletes
If you are an endurance athlete, then you should love the DC area! During training, I'm usually reminded how well the DC area prepares endurance athletes to race anywhere in the country, or the world for that matter. Barring the extreme courses that border lunatic fringe, DC proper in itself provides ample hills and undulating courses to meet the challenging terrain offered by other U.S. cities. I consider being a DC resident an advantage for training purposes, so I hope you never get turned-off or discouraged by what our trails can do to your running pace (take it with a grain of salt), which is certainly another reason I am not a strong proponent of Garmins (too much emphasis on pace). Once you go even as little as 15 miles outside the city, the rural areas of MD and VA offer some intense hills and spectacular courses.
I've raced in 15 or more different states, most more than once, plus 3 other countries, and I can honestly say that I've never felt under-prepared, even if any of those other courses were considered "hilly" or "challenging." I know I'm far behind many athletes who have raced in more corners of the world than I have, but if they originate from this region I'd like to think they'd agree with my sentiments. I've done training in other states and I've never felt that the DC area paled in comparison to where most road races and triathlons take place. I thought Ironman St. George (UT) in May 2011 was the toughest course I've ever tackled, but I know Skyline Drive in Shenandoah Valley had me more than adequately prepared. I've coached athletes of all backgrounds, skill levels, and distances, and most of them have done quite well in their races around the world, even if the course was deemed to be daunting at face value.
The Take Home Message is that if none of what you just read resonates with you personally, then you need to explore the area more! Pack your run shoes more often when you travel and head off the beaten (touristy) path. You'll notice there aren't many places you'll travel to that offer as many challenging routes as our region. Also, if you train outside year-round in DC, then you also know the weather in other states won't keep you down. It gets muggy here in the summer, so if you've been acclimating well, then your mid-summer vacation to another hot destination might actually allow you to have some higher-quality workouts.
You can try treating some weekend workouts as special days so you can go looking for the spectacular sites. Finally, on the other hand, you also need to make sure you aren't doing all of your key workouts on rolling terrain. You need to ensure you have solid long runs on flat courses, which is related to another topic/blog of Breakthrough Performances.