Oh, gosh. We took DS the first time when he as about 8-9 months, so just a touch younger.
Make sure you bring plenty of diapers and wipes. If it feels like too many, good! They're a small fortune down there. Ditto on baby food, I packaged it really well, think bubble wrap, paper towels and ziplock bags, and prayed it wouldn't break. It didn't. Although probably, you could order from one of those grocery services, ship it to yourself, or if you're renting a car, buy it down there to make it easier on yourself.
Have some little toys for the baby to play with at restaurants. This really helped to keep our DS distracted during meals. Although mostly he was very contented to just sit and people watch, he was that kind of a baby.
Make sure you have multiple changes of clothes with you when you go into the parks. I had one incident, granted he was older, where I ran out of clothes and ended up running from Italy in the World Showcase to MouseGears. And back. That was an interesting night, of course we were in the middle of dinner.
I can't think of anything else right now, but if I do, I'll post it.
