If it's just one file, just edit it. The only reason for a script is if you need to do it several times.
To write a script, you need to define the decision logic. e.g.: Are you going to act on every line containing "Mexico City"? Or maybe you just want to change every instance of "5,1-7:+1:9,24-30:0" to "4,1-7:+1:10,25-31:0" ..?
Here is one of many possible solutions:
sed '/Mexico/s/5,1-7:+1:9,24-30:0/4,1-7:+1:10,25-31:0/ filename > newfilename
This makes the replacement on every line which contains "Mexico"