Welcome to Apple Support Communities
If you don't want a iCloud mail, just don't turn on iCloud Mail or Notes. Those are the services that uses a iCloud mail address, so if you have these options unmarked, you won't have a iCloud mail address. You need a iCloud mail address to sync notes between computers and devices, and in case you want a new mail address, but you can continue using your Gmail mail address without any problem.
If you want to sync your iCloud data with your PC, use iCloud Control Panel or go to http://www.icloud.com