There are 4 Marriott-brand properties grouped together within 1/2 mile of MDW, and they're fairly consistent with similar properties everywhere else. They are all in either Chicago or Bedford Park (which borders on Chicago near MDW).

It is true that it is not convenient to walk to the terminal or the el. In fact, the el station is about a mile away from these properties, but a 24-hour shuttle bus regularly services all of them and is prominently mentioned on their web pages.