I was just wondering what network optus roams on inthe USA? Ie T-Mobile, At&T, Verizon
I am just trying to find out what network so that i can look up the coverage maps for that provider to see if i would have service.
You should make better use of google if you want to travel .
That would get you to this quite detailed page
But perhaps consider grabbing a SIM card over there (or order one online before you leave) The data allowances will be much greater and cost less and you don't run the very real risk of accidentally racking up roaming fees higher than the cost of your airfare (even with travel packs). Use something like WhatsApp with your mates and family for sending back quick snaps and keeping in touch etc.
Have a good trip.
PS Travel Tip - Download local data for of google maps to your phone for the areas you want to visit. That way both the map and directions / search features will work even if you have no reception (and you save a lot of data)