I spent 3 weeks volunteering with organization Green Life Project. It took place in Gunung Leuser national park, close to village Batu Katak. And on the see at Palau Sikandang island.
In Indonesia, you can buy local sim card. If you want full service, with calling and SMS, then you have to register and it is complicated. When is only for data, you don’t need to register and you can buy card almost at any shop. I used Telkomstel and that worked fine. You can use application My telkomstel to find out how much of GB’s still remaining. New SIMcard has 8GB, but only 2GB can be used for public internet. Another data pack is possible to buy at MyTelkomstel application, but you have to top up credit first. That can be done in Indomaret shops.
If you wanna see orangutans rather go to Ketambe than to Bukit Lavang (orangutans are fed here, which is not good for them)
What to take home: palm sugar – gula mera, turmeric root, coffe, pecel – peanut sauce, coconut products
If you need shared car to get somewhere, ask at your hostel.
Drinkable water can be refiled at hostel or in water treatment shops in village/city.
From my experience, coral reefs are in better condition on more distant islands from mainland. I was on Palau Sikandank, where it was quite OK. Reef was almost dead close to Padang. Use coral safe sunscreen to protect corals. Do not throw cigarettes to ocean, it kills animals coral reef and see animals.
At bigger cities you can use Uber like service which is called GoJek. Or Grab in Medan. Use application on phone. You can order motorbike or car. Cheapest ride on motorbike was 4000Rp.
For flight booking you can use local application Traveloka or I used Cheapflights, which was sometimes cheaper.
It is better to take Euros for exchange. Check rate before exchange, sometimes they offer you bad rate. At ATM you can withdraw maximum 1.5 mil. Rp.
If you want to go snorkeling, it is better to take your own equipment. Quality of rent ones is low. If anything bite you in sea, try to use vinegar.
Some mosques are calling for prayer very loudly at morning around 5am. Take ear plugs if it might disturb you.
People are usually Muslims or Christians (on Sumatra)
It is very useful to learn basic words, at least numbers (make some cheat sheet), local people does’t speak English so much.
Sumatra looked quite safe. Anyway I have heard about stolen motorbike and bags at Bugus waterfall. Local people are very friendly and like to take pictures with white people 🙂
VISA – If you stay less than 30 days, you will get Visa on arrival. If you need to stay more, you need to get Visa at embassy. If you want to stay longer, than 60 days, you need to extend Visa, which usually takes 5 working days and you can be asked to visit embassy more times than once for collect Visa. Especially in Medan it takes more time. They are quite strict about working hours. Morning they accept requests for visa, afternoon is time for collecting visa. You can extend visa in different city, which could be faster. Possible option is to flight out of Indonesia and directly go back to get new Visa on arrival. Or if you come by boat, I heard that you have to go to embassy to report yourself, but you can take some time to do it. For getting Visa you need fly-back ticket. If you do not know how long you are staying, it works that you make fake flight back ticket.
Jungle trekking – I can recommend to buy local rubber shoes, which look like football boots (max size is for leg size 43). Make one hole in back so water can get out if you go in river. Than take very long (underneath knee) socks, which are from very consistent material to prevent bloodsuckers to bite you. If it happens, you can pull away it or use salt and it will release itself. Long trousers are than not necessarily. It is very damp at forest. Use sweatband. One walking pole can help.