score:8
You can tweet to your account via SMS (https://support.twitter.com/groups/34-apps-sms-and-mobile/topics/153-twitter-via-sms/articles/14014-twitter-via-sms-faq), and then link your Twitter account to Facebook, so your tweets get published on your timeline (https://support.twitter.com/articles/31113).
Upvote:3
Rory, where abouts will you be travelling to - just one country or several?
Hotel WiFi is also becoming more and more common; I live in the US, but was travelling around the north of UK and Amsterdam/Brussels earlier this year, and many of the hotels now have free WiFi for guests. I was able to use this to log-on to facebook with my android mobile via the wifi without having to use data roaming. This does require having a smartphone or laptop can can use the wifi, however.
If visiting just one country, one option might be to purchase a 'cheap' $20-ish or less SIM card (available at most high street cellphone stores - usually come at a starter price that you can top up at newsagents later if needed) and use that to send SMS from, which could work out cheaper than sending SMS from your own account, since you won't be hit with additional roaming charges -- assuming FB has a corresponding mobile access number for your destination. The catch with this is you have to swap it for your regular SIM in your phone, or just stick with the 'foreign' SIM while travelling - which would be cheaper for making calls back home too (though likely not as cheap as using free hotel wifi to skype!).