Hi,
I have been travelling in Sumatra since 1997 and have had about 7 trips there and am planning my 8th trip there from June 2010.
I have almost always travelled alone as a solo female and never encountered any problems.
In 2006 I spent 3.5 months travelling through West Sumatra, visiting new places as well as revisiting old haunts and cathcing up with my numerous Sumatran friends.
I also spent quite a few weeks in North Sumatra visiting Bukit Lawang, Tangkahan, Lake Toba, Brestagi and then moving onto Aceh- ketambe and bussing it right up the centre.
Travelling in Sumatra is not 100% easy but it is not too bad.
For instance if I was you I would do either North Sumatra and fly from Medan to Padang or the other way around- Padang, Lake Maninjau, Bukittinggi etc and then fly from Padang to Medan.
2 hr plane trip compared to a 20 hr bus trip from Padang or at least 17 hrs from Bukittinggi.
My photos from my 3.5 month trip through Sumatra 2006 can be viewed at http://www.webshots.com/user/ppamela2006
This trip was aprt of a 5.5 month trip through Indonesia.
I am planning a similar trip from May 2010.
Here is a search on another forum I post on with info' about West Sumatra
http://www.lonelyplanet.com/thorntree/search.jspa?threadID=&q=West+Sumatra&objID=f23&dateRange=all&userID=pPamela&numResults=15&rankBy=10001
and the same for North Sumatra
http://www.lonelyplanet.com/thorntree/search.jspa?threadID=&q=North+Sumatra&objID=f23&dateRange=all&userID=pPamela&numResults=15&rankBy=10001
Happy Reading and Feel free to ask me any questions you wish.
Pamela- huge Sumatra Fan.