You can install iOS11 on any phone without any developer account, need not to wait till the public beta.
- Download and install iOS11 Beta profile from this url: https://drive.google.com/open?id=0B6yYIT6yt6MpZ1BVQ2pmOVhDNlE (remember to open this url from your iOS Device. )
- Restart your device as prompted after installing beta profile.
- Check for update after restarting
- Download and install iOS11 Beta