Regardless of the time of day you decide to fly, the ticket price will remain around the same. Book flights from Cancún to Bali as you normally would.
Due to multiple factors, expect to potentially pay more when booking in August. For low rates, November can be a great choice for travel to Bali. Flights to Bali from Cancún in November are about $1,379 on average during November, but can be found for as low as $1,110.