Great start, @pachyderm pro; glad to have you in the game 
Your list looks good except for this one:
This species is not native to Mexico and therefore doesn't count, so you're at 20. Additionally, whatever tamandua you were planning to see will be Southern which also doesn't count. Ocelot and White-nosed Coati would count.
Comparing your species and institution lists everything looks fine to start; just remember to keep track of where you saw each animal on a go-forward basis.
Your list looks good except for this one:
21. Hoffman's Two Toed Sloth (Choloepus hoffmanni)
This species is not native to Mexico and therefore doesn't count, so you're at 20. Additionally, whatever tamandua you were planning to see will be Southern which also doesn't count. Ocelot and White-nosed Coati would count.
Comparing your species and institution lists everything looks fine to start; just remember to keep track of where you saw each animal on a go-forward basis.