To a great extent it depends on where you are "checking in", On the US mainland or in Central America.
If you bought through a broker or agent, they can give you printed terms.
Here's the scoop per their website:
Economy Class
Carry-on baggage: 1 piece weighing up to 22lbs/10Kgs, and measuring up to 45in/114cm.
Checked baggage permitted: 2 pieces, each weighing up to 50lbs/22Kgs and measuring up to 62in/157cm.
Baggage pieces that weigh between 51lbs/22Kg and 70lbs/31Kg, and measure up to 62in/157cm, have an additional charge of US$50 each.
Baggage pieces weighing more than 70lbs/31Kg, but less than 100lbs/45Kg; or measuring between 63in/160cm and 85in/215cm, are considered standby bags and have an additional charge of US$100 each. In this case, if the same bag is both, overweight and oversized, only one charge will apply.
Read about the new charges for overweight and oversized baggage,
effective June 15th, 2009, here:
Taca.com