Instructions
Go online to the official website of "City Bus Simulator" and click on the download option in the upper navigation bar just below the image of a bus.
Scroll down to the information posted on the site dated 10/29/2009 and entitled "Hotfix for version 1.3. English." Read the text explaining the language issues that the program will solve.
Install the hotfix by double clicking on the "CBS_Hotfix_for_Version_1_3_english.exe" link in yellow font. When prompted as to the game's destination folder on your PC's hard drive, choose the default option. Select the "City Bus Simulator 2010" directory by clicking OK.
Complete the hotfix installation process by selecting "all" when prompted. The game should now be completely in English. Play the game as normal to check whether the hotfix has worked. If not, download the file again.