Hmm, it looks like the closest Metro station to your hotel is Crystal City. From there you can take the Blue Line train just two stops up to Arlington Nat'l Cemetery. The Blue Line can also take you into the city to see the various Smithsonian Museums and the monuments, from the Smithsonian stop, I think (some locals can probably chime in with their further detail on this). This is all assuming that you are comfortable with some walking; the Mall is somewhat large, and the monuments are quite spread out. I do recommend seeing them at night; a very nifty and very different experience than seeing them in the day. ^