Try the following:
- Turn off your Wi-Fi.
- Turn on the mobile data (Located under data usage or mobile networks after you hit more...)
- Go back to system settings.
- Scroll down to system updates.
- Press update profile (the phone may restart after this).
- Update the PRL as well (the phone may restart after this).
- Test the service once again.
In this Zip Code the coverage can go from Best to Fair. Also, while you're travelling its possible that you not receive a stable coverage.