Q: I have just got my iphone 4s and the language is not english. I dont have a sim yet, will this fix the problem?*

The very first screen you saw when you powered on your device should have asked you what language you wanted. Did you not select English? A SIM will not change this.

There is a language setting on the iPhone that you can change at any time. It has nothing at all to do with the SIM card. It's under Settings --> General --> International --> Language.

This gives a good explanation, with photos:
http://support.apple.com/kb/HT2371?viewlocale=en_US&locale=en_US