You can take bus 26A to 新馬路Avenida de Almeida Ribeiro Station. Then walk through Senado Square to the ruins. Another option free of charge. Take Venetain's free shuttle bus to Macau Ferry Terminal and then change to the free shuttle bus to Hotel Lisboa. Then walk at most 20 minutes to the ruins. City of Dreams beside Venetain has free shuttle bus to New Yaohan which is close to Senado Square too. You can walk to the riuns then.