I usually learn some words in a new language for every country I visit. Do the Thai like people talking Thai or do they prefer English?

When you arrive in Thailand you shouldn't really have a language problem if you stick to the main tourist route. The hotel staff will know "hotel English", the taxi driver will know "taxi English" and the shopkeeper will know "shop English". However, once you start chatting away about something unrelated you might have a problem. Also, once you leave the major cities and start going to places which don't receive many tourists you will again be presented with a few problems. That is why we are here to help!

I think your first stop should be our:

http://www.learningthai.com/useful_phrases.html

At the very least you should learn these words.