As far as I know it should not affect your ability to use FaceTime. Why? Is there No FaceTime app on your iPad? If you bought the device in a country where FaceTime is restricted - the app will not be on the iPad and you can not download it.
If you had the app and now it is gone ....
Swipe from screens to screen to look for it.
Check Settings>General>Restrictions and make sure that you didn't restrict it.
You can also reset the home screen layout and the icon will reappear - but the home screen will return to the way that it looked when you first activated your iPad.
Settings>General>Reset>Reset Home Screen Layout.
You are having activation issues. You might try signing out of your Apple ID on the iPad, restart the device and then sign in again and try setting up FaceTime again.
If FaceTime is turned on, turn it off. If it hasn't accepted your ID for verification you don't need to sign out here. However if I am wrong about that, sign out in FaceTime. Tap on you Apple ID and sign out. Otherwise go to Settings>iTunes and App Stores>Apple ID. Tap your ID and sign out. Restart your iPad. Then go back to Settings>FaceTime >On. Then try to sign in here again and see if your ID will be verified by Apple. Don't forget to go back to the store settings and sign in there again as well.
These two support articles might be of some help.
Using FaceTime http://support.apple.com/kb/ht4319
Troubleshooting FaceTime http://support.apple.com/kb/TS3367
The Complete Guide to FaceTime + iMessage: Setup, Use, and Troubleshooting
Troubleshooting FaceTime and iMessage activation
Using FaceTime and iMessage behind a firewall
iOS: About Messages
Set up iMessage
Setting Up Multiple iOS Devices for iMessage and Facetime
FaceTime and iMessage not accepting Apple ID password
Unable to use FaceTime and iMessage with my apple ID
For non-Apple devices, check out the TextFree app https://itunes.apple.com/us/app/text-free-textfree-sms-real/id399355755?mt=8
I am using Cellular service in India for my iPhone 5. When i try to use FaceTime it doesnt work, however when i try this using wifi it works absolutely fine.
As far as i am aware this was one of the enhancement in iPhone 5 to support FaceTime over any Cellular Network. Please suggest
India is growing market for iPhone , If this feature will work here it will be a big BOOM