So if it says "No Signal", I won't actually get a signal?
Going by Straight Talk's maps, I should have coverage everywhere. However, I don't think that's true as AT&T has no presence in Eastern Iowa (around Vinton) and in Flagstaff, AZ which are two places I go to.
Also, I checked out
OpenSignal - Crowd-sourced Cellular Coverage Maps for the world. which also says I should get signal. OpenSignal shows that AT&T has more towers and more coverage in Omaha than Sprint does and that Sprint has the worst coverage in the city, AT&T has 2nd best. This information doesn't take into account that AT&T added 4G towers here as well (which ST obviously can't pull from) so, unless AT&T removed some towers, then it should be better.
There are so many sites saying I should and shouldn't get signal, I'm starting to think it'd be best to just try the service anyway just to check.