Was reading an article the other day about it and in Jelly Bean (4.1) the download max is 80mb (US article) so they were complaining that with such a small limit its pretty useless in the states, UK not sure how much can cover with that but still will be pretty limited.
At the moment it seems its impossible to download the whole country. What I don't understand is why you have to select a square are to download when surely it would be better to be given the option to "download my navigation route and an extra 5-10miles each side of route"
I doubt they will tailor to your situation with no free data as that defiantly doesn't seem to be the norm with smartphone owners these days