Hi @AnnieP
I rarely visit the Samsung Board, so have only now seen your query, and rather fear I may be too late. There is general advice on travelling abroad on http://www.vodafone.co.uk/discover-vodafone/managing-my-costs/travelling-abroad/ and specific information on Vodafone Data Traveller on http://www.vodafone.co.uk/shop/pay-monthly/travelling-abroad/vodafone-data-traveller/index.htm - it's my understanding that on a SIM only contract you would qualify for that.
I'm A PAYG customer, and unfortunately PAYG doesn't work in most areas of China, so my experience on a trip to China early last year was largely a blank as far as my phone was concerned! But it might be a wise precaution to get your phone unlocked before you go, so that you could use a local SIM if you had to.
The only other thing I should mention was that, although I found wifi in some hotels, access to all my webmail was blocked - no access to Gmail, btinternet, or live! Though they had missed one trick - I could still use PMs via this Forum! I managed to get a message through to my brother, who registered with the Forum, and I then had one contact route open to the UK!
Good luck with your travels!
Further thought - I can't think of any reason why an S2 shouldn't work. There shouldn't be any problem with frequencies.
