Though travel in the wet season is possible in most parts of Indonesia, it can be a deterrent to some activities and travel on mud-clogged roads in less developed areas is difficult. In general, the best time to visit is in the dry season between May and October.
The Christmas holiday period beings a wave of migratory Australians and there's an even bigger tourist wave during the European summer holidays. The main Indonesian holiday period is the end of Ramadan, when some resorts are packed to overflowing and prices skyrocket.