Another idea from Alexandria or Crystal City is take the Yellow Line past L'Fant Plaza and get off at Archives. Then catch the Green Line to the ballpark. Archives is much easier and less crowded than at L'Fant Plaza.
Now that the crowds are bigger, you really ought to consider walking to Cap South if you are catching the Orange. If you are with kids who can move along or adults who don't mind a walk, it is pretty easy, you can get a seat, and you don't get the sardine effect on the platform.
