Those USA passes are great for lite to moderate users.
If you are a heavy user, your phone is unlocked, and you don't mind giving up your phone number for a the week (got a second phone?)...... Check out these prices from a Vancouver based company running on the TMobile network....
Roam Mobility SIMs and devices are available at London Drugs, airports and duty-free stores before you enter the USA.
Love Google Maps and researching my day itinery on the go.