Howdy, potential future neighbor. I'm a six year resident of the 1300 block of R St., and I enthusiastically recommend it. My father lived on the block in the late 1980s, when it was significantly sketchy, and I recently returned quite surprised at how far it's come. As a single woman, I have never felt uncomfortable here.
The 1300 block of R Street has at least two $1 million + residences. There are a lot of young professionals here and some older couples as well. Our block also has a homeless shelter and group housing for those whose mental disabilities or addictions prevent them from living on their own. However, both the shelter and the group housing are run incredibly well, and I have not known them to cause problems for their neighbors. Your other potential neighbors within a one block radius include a large swanky new condo building, several churches, and an elementary school.
Our biggest crime issues are theft from vehicles and muggings. The muggings tend to happen after 11, and usually victimize folks walking alone. I've never personally known anyone to get robbed, but the statistics don't lie. Staying off your iPod or cell phone as well as staying sober can go a long way toward helping you maintain an awareness of your surroundings. Theft from vehicles only happens when there is something worth stealing within plain sight. Also, evidence of something worth stealing -- like suction cup marks from GPS systems -- has attracted thieves to cars.
That said, it's a fantastic neighborhood. There is so much to see and do on 14th St., P St., and U St. The location also puts you within walking distance of Adams Morgan and Dupont Circle, two other fun neighborhoods.
If you want more info., there are two blogs I'd recommend. The first is Borderstan
Borderstan and the other is 14th & You
14th & You (which my husband is currently running).