There is bus service in South Lake Tahoe, and in the Winter Heavenly Ski Resort has its own bus service, which is free this is meant to shuttle skiers to and from their hotels and motels. There are also taxis, however these are in very high demand in the winter, and waits of 30-60 minutes are not uncommon in peak times.
All major locations around the Heavenly Village area such as the stateline casinos, are within walking distance of each other. There are underground walkways between the major casinos.