Belize is very US friendly, so, if caught they would be extradited back to the US.
Three ways to get to Belize: 1) Air - too risky 2) Cruise ship - too risky 3) Drive through Mexico - risky but possible.
There are many places in Belize to hide out but more and more Americans are there, even in the South where the Mayan villages are. Belize is a very cheap place to live. They could use a "missionary" cover for several weeks at a location then keep moving. Word gets out when an American is around.
I consider Belize a 2nd tier possibility but a reasonable one.
The above is my opinion only.