You can get a 60 day visa in your home country ( you have up to 3 months from date of application to enter Indonesia where you will then get your 60 day stamp) or at one of the countries close to Indonesia like Penang, Kuala Lumpur, Bangkok, Singapore. I have received 60 day visas from both Singapore and Penang in 2006 without any problems.
Usually takes about 3 days and you will need a passport that has at least 12 months left on it, two passport photos, photocopy of the first page of your passport and money to pay for the 60 day visa.
Make sure you are well dressed to apply for the 60 day visa in places like KL. There have been many cases over the years where scruffily dressed travellers have been refused visa application.
Since last year 2007 one has been able to get 60 day visa with the same number as the social visa no. 211. This simply means that NOW you are able to extend your 60 day visa in Indonesia at 30 days a time up to 4 times nowadays giving you a total of 6 months in my favourite country.
The one thing you will need is an Indonesian person who will sponsor you to get the extension ( no cost to them, but I believe it would be a nice gesture on the part of the traveller to give the Indonesian person at least 100,000 rupiah for their help).
Legal cost of the extension is 250,000, but you will find corruption is still alive and kicking in Indonesia particularly North Sulawesi and Bali where it will cost a lot more.
Also be aware you will need to go to major cities to their Immigration offices to apply for extension.
Re: counting your days- you must count the first day as one dayeven if you arrive at one minute to midnight and the same when your 60 days is due to expire.
Suggest you organise your extension or at least enquire about it at least two weeks before the 60 days expires.
My suggestion would be to stay in Indonesia- do Sumatra and then travel down to Bali or fly from Medan to Jakarta to Bali.
From my point of view and experience you will have such a memorable experience doing Sumatra and then doing Java/Bali immediately after- the comparsion of the places will be mind blowing.
Leaving and going back into Indonesia will lose a lot of that impact besides the fact it will be costly.
Would love to know where you plan on going to in Sumatra- one of my favourite areas - have been there so many times and spent 3.5 months there in 2006.
Aceh- i.e. Ketambe is definitely worth a visit and then bus ride up through Aceh to Banda aceh stopping off in Takengon is great too. And Pulau Weh off Banda Aceh.
Java is wonderful as well- lots of temples Borobudur in Central Java and great places like Gunung Bromo and Kawah Ijen East Java.
If you have anymore questions and would like to contact me personally just send a PM and that applies to anyone else who would like more information.
Pamela (who has visited Indonesia 8 times since 1997 and had two long trips 4 months in 2000 and 5.5 months in 2006.) Photos from 2006