Xunantunich is one of the most interesting of the ruins near San Ignacio. The setting is lovely. You can climb the main tower and the view from the top is stunning. Much of the carvings on the face of the buildings are still intact (although what you see is actually a replica protecting the actual face). It is one of the best ruins in Belize (although Tikal is probably even better in Guatamala). To get to the ruins you can go with one of the tour operators or grab a bus (10 minutes ride - $2B) in San Ignacio and get off at Succutz/Benque Viejo del Carmen.  There is a free ferry across the river.  Expect a 45 minute walk to the site itself.   It closes at 4:00 pm.