Questions on Google Maps

I'm thinking about ditching my TomTom in favor of my phone and have a couple of questions on Google maps.

Frist, I've saved a map of my city to the phone. Will it use that by default rather than using data?

Also, is there as way to save locations and call them up when needed?

 

Yeah, as I played around with Maps I found it wouldn't use offline maps to navigate.

I don't have a huge data plan, so I'd like to find something that could store most of the date on my phone. I don't mind using the data connection for things like traffic and the like, but would like something that does use some stragegies to limit the amount of data used.