Are you renting equipment at the landing?
Go early and talk with the people coming off boats that are carrying fish - ask about the water conditions - what they did to catch their fish, were the fish caught during trolling or bait fish.
Go into the tackle shops at the landings and tell them your new - ask what tackle setups are working best. You'll be surprised on how much information you'll get.
Tuna fishing can be a long boat ride with little action and at other times wide open fishing getting so tired in an hour or two you need a break.
Yellowtail would generally be a different type of fishing than tuna (bluefin - yellowfin - albacore). Not saying you won't do both, especially on a 3 day trip to Mexico.
Don't forget to enter the pool... Bring back some pictures

Good luck!