Hi, Wendy. Congrats and welcome! This is an amazing site with lots of great info! It is a very cool ceremony to be in Mexico with a Spanish/English ceremony. For the legal aspect, quite a few couples get married in the states right before they leave, but it doesn't seem like to big of a deal to just do it there. Whatever you prefer!
Have fun planning and let us know if you have any photography questions!
Best wishes,
Katie