That sounds like a very pleasant place to live! We would say in English, In West Java. Not "on." If you had a map of West Java lying on a table you could put your finger "on" West Java. "In West Java I can go everywhere by motorcycle without worrying about rain." Or "In West Java I can drive my motorcycle all the time without worrying about the rain." "I can go everywhere by motorcycle." So we go "by motorcycle, or by train, or by boat or by car" But we go "on foot" if we are walking.