i found this video so helpful, to update maps on garmin gps.

To Make it speak street names:

1. From the Main menu, select ‘Tools’.
2. From the tools menu, select ‘Settings’.
3. From the Settings menu select ‘Language’
4. From the Language menu, click on the button under the ‘Voice’ label.
5. Select a voice where the name ends in ‘(TTS)’. If the voice is not labeled as ‘TTS’ it will not speak street names. Click OK a few times to accept your new preferences.