Ticket Honduras-Lima, kopen in Mexico City?....

Hello,
I live in Amsterdam and I’m flying to Mexico City in July, I will go to guatemala maybe and Honduras in august for diving with a friend.

In September I will fly from Honduras (or somewhere around there) to Lima to do volunteer work in Bolivia for 2 months.

 Question: I doubt when to buy the ticket from Honduras to Lima. The   foundation is expecting me so I need be sure about it, but I do not  want  to pay too much. 
 Someone with a lot [Peru](http://www.tripadvisor.com/Tourism-g294311-Peru-Vacations.html)/Bolivia  experience told me it's much cheaper  to buy a ticket over there. And  she said it's no problem to book it two  months in advance. If that's  true, I will buy it the first week I  arrive in Mexico City. If not, I  will buy it in advance from the [Netherlands](http://www.tripadvisor.com/Tourism-g188553-The_Netherlands-Vacations.html).
 What are your e xperiences with buying tickets from Middle to [South   America](http://www.tripadvisor.com/Tourism-g13-South_America-Vacations.html)? (Around 2 months or shorter in  advance)  and what are the prices over there? Here they are around 400  euros.


 Thanx!