Take a look at
* CoPilot GPS - Plan & explore! - Android Apps on Google Play
I think once you start using that app, you will forget about Google Maps. I have.
it will download the entire North American map database as one file, and it allows you to specify "internal" or "external" storage. Or, you can pick just one state or region.
The file I downloaded is something like 2.5 gB in size.
but, once it is done, DATA is not ever needed again. The stuff it has available in that database if awesome.
and since it is all on the phone, it is extremely fast at finding anything you want to search for.
Very configurable for proximity alerts, ie, what type you want to be alerted on, and how far in advance you want to be alerted.
Google don't even come close to being as versatile as CoPilot is.
I have the Pro version which IMO is cheap at $9.99 for a lifetime of updates, and will provide you "turn by turn" audible directions from the lady or guy of your choice. You can install different voices...
Oh, make sure DATA is turned OFF and you use WiFi to download the maps.... expensive if you don't.