You will have to comply with the agricultural/livestock health requirements to import your animals. Check the Mexican government websites for the details. If you bring them in with your trailer, the trailer will be imported as a unit with your tow vehicle. As such, whenever you leave Mexico with the vehicle, you must take the trailer with you or you won't be able to get the 'importada temporal' sticker removed by customs, as required and now being enforced. It is a wise move anyway to avoid being prohibited from re-entering Mexico with another vehicle in case of loss of the original one. So, if you had planned on trips to the USA without the trailer, forget it. You can't sell the trailer or the tow vehicle in Mexico and permanently importing them is more hassle and expense, for an expat, than it is worth in most cases.
well then .... suggestions? commercial equine transport? what i'd like to do is ride south from about puerto vallarta along the coast and find our "spot". so if i had them transported to vallerta would that work?