There is a highway that goes through Mexico to Belize. Don’t go to Guatemala.
I think the exchange rate for the US dollar in Belize is 1 to 2.
It is the Pan-American Highway System. BUT, don’t stay on it otherwise it will end in Panama. But, there is a highway that will leave the main highway to travel to Belize. In a climate emergency like this a USA drivers’ license will serve to prove ID. The Mexican authorities should understand the issue. Belize can be strict about border crossing but they will understand life and death. Belize doesn’t want drug traffic.