that depends on two things:
1) how fast is the network link between the two offices?
2) do you want everyone to be able to access their email if the office goes down or just the Peru employees?
if your answer to #2 is just Peru then you could setup a second exchange server in Peru and move their mailboxes to that server. If it is everyone then you will need to setup a cluster server so it is an exact duplicate of the server in the US. You could use programs like Neverfail or DoubleTake to do this. They will basically clone your first server to your second and setup a heartbeat which makes the servers listen to each other. When something changes on the first server it will be copied to the second. If the first server goes down then the second will take over within a few seconds and be the primary server. But this will be laggy if the line between the offices is slow. You would need to talk to Neverfail or DoubleTake to see how fast a line you would need to do this reliably.