Is it usually allowed to reserve a hotel in arrival? Like cash face to face without an online reservation?
Yep, but you pay the rack rates in this case. Cash is always welcome, if it's IDR.
Yes, as long as they are not fully booked.
Also , when you decide your hotel, may I suggest to go online and book that way , even for the same day. This will be cheaper than just going to the hotel and paying the rack rate. If your issue is being unable to go online , use the hotel's wifi. I have even asked to use a business centre of a hotel to book and they were very helpful...that was in Penang though.Edited: 23 May 2018, 06:27
Of course as long as rooms available. Ask the rate at front office.