I just came back from Colombia and Peru 2 weeks ago.
The Mobile 09 did not work in both countries; the phone found up to 3 networks, registered with each but then was for emergency only or it did not let me make a call. I could not be reached either.
In Peru I was using my Motorola V3 with a German T-Mobile which is rather expensive.
In Colombia I bought a Tigo Sim card for 10,000 pesos (US$ 5.00) which is expensive for making calls abroad, but reasonable for messages and local calls. Incoming calls are free.
I would suggest to buy a local SIM card. Visit
www.tigo.com.co or
www.movistar.com.co - they have packages including the phone for $ 30. If you have a quad phone you can buy the SIM only.
For Peru I recommend the Claro chip for 30 soles ($ 10) which is also free for incoming calls. Neither of these cards will work in the neighbouring countries. I tried T-Mobile in Ecuador last year which did not work.
Wolf