Here's what I plan when traveling next - I use Google Voice (GV) as my main cell number anyway. I use PBXes.com (can do this with VoIP.ms or other providers as well) and have the call go to an IVR (recorded message) which says that I'm travelling and am currently X hours ahead/behind of EST right now, press 1 to continue the call or 2 to leave a message.

This really helps in cutting down inadvertent calls in the middle of the night, and still lets me receive important calls; casual people will leave a voicemail which gets emailed to me (using VoIP.ms).

Requires a bit of setup, and is very flexible in that I can have the call forwarded to a local SIM number instead if needed.