HI
We just used the 10 day phone, text & data add on & it was great. We didn't go east coast but went to many states in the USA west including:
Washington, Oregon, California, Nevada, Arizona, Idaho, Utah & had good ATT most of the time. The only weaker signal was in remote parts of Arizona/ Utah.
We didn't do any speed test as conserving data but used for google maps several times with no issues.
We were not sure how much data we'd need & our trip was 13 days so we decided to start with one 10 day Public Mobile Tak, text data, plan & start it at hotel on 1st night on my wifes phone (not unlocked). Then on my unlocked phone use R**m's 30 day data 2Gb. I've used them before including a Yellowstone trip & found gaps in coverage on that route (but seemed ok this time).
Public Mobile worked really well for us & we didn't use up even the 250 mB data despite doing some google maps, disneyland app etc.
We did use some tricks to reduce data such as storing off line google maps for the next days driving while at the hotel or wifi. I had also 'printed to pdf & stored in downloads' many of the e-receipts/ reservations etc so i wouldn't need data to retrieve addresses.
