Look at GSM world for the Indonesian GSM/3G carrier info to see coverage maps and whether they include 3G/EDGE service. It's out of date, but it looks like at least one carrier offers 3G/HSDPA @ 2100-
http://www.gsmworld.com/roaming/gsminfo/cou_id.shtml

There are broadband laptop cards that include all the necessary frequency bands for global roaming. In your case I believe all you really need is 2100. You could check the ATT site (for example) as they carry quite a few from what I remember. Just found it actually. Here you go-
http://www.wireless.att.com/cell-phone-service/cell-phones/pc-cards.jsp

(I'd prefer a dedicated non-USB device if I had the correct card slot.)

They would also be able to assist in finding a roaming partner (if available) for accessing services you require where you will be staying. If you're too far from the beaten path it might be tough though.

hth,
Pedro