Once downtown, those without a car can catch a free trolley, call for a cab, rent a bike, or hoof it (downtown is incredibly walkable). The Regional Transit Authority runs buses and rail routes into surrounding neighborhoods and inner-ring suburbs.
And, with two major airports in the region, a variety of flights fly non-stop to the area.
Clevelanders, in general, are a friendly bunch, so when in doubt, ask around. You can also stop into the Visitor Center at 334 Euclid Ave, where the concierge team can tell you exactly how to get wherever you want to go.