I plan on bringing things for my centerpieces with us, we are going to pack as much as possible and then pay for a few extra suitcases for our parents/siblings to bring down... it is going to cost a little bit for each of the extra suitcases but shipping there will cost just as much and probably more.... i also am a total control freak and feel much better bringing my things rather then shipping them so that i know they get there safely, and then i don't have to worry about customs holding anything up...
back to the legal ceremony thing, i think thats a choice that you have to figure out what works best for you both... my fiance and i wanted to do it the day before we left because we could not imagine coming home from our dream wedding and not being "married", having people say congratulations and not being legally married to us was just not something we wanted to do. fortunately for us i work for a court and the judge is going to do our legal marriage on valentines day (day before we leave), we are going to keep it very quiet and then treat our wedding in mexico as our real wedding date. i am not worried about not having the emotions on the actual day because i know that we both will, i mean after all it is our dream wedding and having our closest friends and family there witnessing everything is going to be the most amazing thing, but now we will be able to come home from mexico and be legit. either way i don't think it is right or wrong (legally marry before or after your trip) just what works best for the two of you!
best of luck with all the planning! its fun and goes soooooooo fast!