The biggest thing people planning the wedding need to realize is that if your wedding is outside of the United States- the customs and culture in the country you are visiting are also different. Specifically, how people respond to "scheduled" events and timelines. People in Mexico have a very different interpretation of time than we do in the United States. Their culture is a lot more laid back and not as concerned with the minutes hand on the clock.
If you are the type of person that needs everything to be "on-time" - a destination wedding may not be for you. In my experience, there is always something that is "running late" hours before the wedding starts...flowers, chairs, officiant, etc...
Most of the resorts do have "wedding coordinators"- but often times this person is juggling multiple weddings or working on other projects at the resort.
My biggest pieces of advice for people...hire a travel agent to help you work with the resort and go into the wedding realizing that all of your plans may be subject to change. If it is outdoors- there is always a chance that it could rain- or something may not show up on time.
Find a travel agent you can trust and has experience working with destination wedding resorts. Their services are less money than you think and will make your wedding planning experience a lot more pleasant and less stressful.
We have a number of great travel agents in the Central Minnesota Wedding Association- be sure to check them out during your search!