1.5 days in Kupang was insufficient for exploration, but it allowed me to save a lot of money on airfare because a flight between Indonesian cities is far cheaper than an international flight from Timor Leste, a politically uncomfortable neighbor. I planned to walk to the main road again and catch a bus going toward the airport, but a hotel guest offered me a ride. From Surabaya airport, I ran into another traveler and together we opted to catch the regular buses toward Gubeng station in the city center. It was surprisingly cheap and hassle free without attempts to scam us into the wrong buses or taxis at the bus interchange. I quickly orientated myself and explored the immediate area around the city center, mainly the Surabaya Plaza and other more modern structures in the vicinity along the Kali Mas river, while enjoying the colorful lighting and an evening stroll. I was surprised to see children swimming in the murky waters to stay cool.
When visiting a new country, if you have time, a great option to see more of a country and save money on airfare is to make a land border crossing then fly out of a major city on the other side of the border. The bus fare is cheaper than the departure taxes when flying and you get to see a different city. This also worked when crossing from Brunei to Malaysia.