I live near Harrisburg, PA and have been to all three of the stadiums (Philadelphia, Baltimore, and DC). Each is served by either light rail or subway stops. It's about the best way you can get to the games, particularly DC, where traffic and parking is a real pain. You'll find that the eastern cities are places where public transit, including Amtrak between the cities, works well. Rail service (train or subway, depending) is present at Reagan National, BWI, or Philadelphia airports. It isn't odd to see people carrying luggage on the trains or subways. Of course, packing light is a good idea, if possible. Most of the standard tourist sites in DC are reachable via the Metro. Independence Hall in Philadelphia is right off a subway stop. Inner Harbor in Baltimore has a couple of light rail/subway stops close by. If you'd want to see some other areas around the cities, then renting a car would make sense. But if you're primarily just going to games and hitting the big sites, then you could basically just use public transit and/or Uber/taxi around. Just get hotels that are in the center city or near stops. (That info would be on their website descriptions.) I'm hitting the July 21 Brewers game in Philadelphia. There's usually a decent smattering of Brewers fans at games there. More usually attend at DC, where there's usually a Wisconsin and/or Marquette alumni chapter event. IIRC, some other Brewerfan people who live/have lived in the three cities, not just visited, even if from nearby. I'm sure they'll chip in with their thoughts.