Comcast will be delivering HDTV to you soon, depending on the county, unless of course you live in the city limits. Comcast will soon be offering Comcast Sportsnet in HD, featuring the Washington Wizards, capitals, mystics, etc. in HD and the Orioles too. If you live within the city itself there is no chance for comcast HD for years and years to come.
Also, seeing your from Irving, TX, we don't mind cowboy fans here, as long as you hate the Redskins, we like you.
As for the DTC:
I live in the city near the towers and get all baltimore channels that are listed above with a rooftop antenna connected to my DTC.
With a good rooftop antenna you should also be able to get Washington channels
27- WETA
34 - CBS WUSA
36 - FOX WTTG
39 - ABC WJLA
48 - NBC WRC
If you are too close to the TV tower you will not be able to get 39 because 38 and 40 drown it out.