Can you trust those?
Probably not much. Consider someone is testing trueGeiger app with radioactive source and logs data to the map. Should you avoid this town since it has a spike on the map?
Conditions change measurable radiation level too. And that happens in many unexpected ways. See an article  in New Scientist on farmers next to Fukushima staying there after the population was ordered to evacuate.
Obviously, it matters a lot what is the source of radioactivity. Please do your research before jumping to any conclusion, especially when looking at a crowd-sourced radiation map. It is rather unlikely trueGeiger will offer such maps in the future.
 Japan’s refusenik farmers tackle nuclear waste, New Scientist, Magazine issue 2855