You can take the 8:30 bus from LaManzanilla and then go into the Prima Bus station and get a bud to Manzanillo that stops by Walmart and the Doriana. Some don't so you need to ask. It is about 50 pesos, then take the local bus to San Deigo bus station Prima and get the bus back to Melaque. There is one that leaves the bus station about 2:30 so you can get the last bus to LaManzanillo. You can also get a taxi ti San Deigo. The bus is air conditioned. Better to go on a weekday as buses get very crowded on weekends.