I can confirm that it's, at the moment, impossible for me to change my username to a proper one without loosing my current points.
I'm now on world_b85zy5cs, I would like Sweo, which I use as nick.
When I first installed the app, I connected via Facebook which caused Waze to create this temporary username for me.
If you used facebook, try the following:
- remove the app
- reinstall the app
- on start, click on login and then login with Facebook
- double check it's your account on wazer->my wazer -> age of your account for example
- follow the faq instructions: settings->waze account-> register -> enter new username, pass, nickname and the email address, which can be the one from Facebook, of if you get an error, any other email.
- login into the client with that username
- on the forum, click on the footer on the "clear all cookies" and login with the new account.
The trick is to start from scratch, login with Facebook to regain the world_account, and *then* create the real account.