How far in advance should you book travel to another country or on a cruise?

My husband and I have never really done any traveling outside the US..and we want to go somewhere next Chrstimas with our 2 year old.
How far in advance should we book something - say down to Mexico, or a cruise?

I would book a cruise as soon as you know you want to go. You will have your choice of all the best cabins. Just make sure that you book with a travel agent (on line or brick and mortar) that will pass on any price reductions to you. You need to ask if they do that before you book. If they say no, go to someone else. I have used vacationstogo. and a regular TA and had great experiences with both.

I am a travel agent and would recommend that you book as soon as you know. There are not huge discounts early but a good travel agent will give you the price deduction! And dont forget you have to have a passport even for the little one!