I've never had any makeup artists in Mexico do my makeup but I have seen people who have had run-ins with makeup artists who work on the resorts that they have their weddings at...anyway, from what I've seen personally, they do tend to have a bit of a heavier hand. If you are a bit picky and are truly concerned (I know I was! lol), then I recommend doing your own makeup. If you're newer to doing makeup on yourself, or you're nervous about doing your own makeup for your wedding, I would recommend that you drop by your local MAC or Sephora and have them give you a tutorial with the products you plan on using. It can make a world of difference.
Good luck!