Skip the trailer. It will be a magnet for transitos in small towns. You can easily ride that bike straight through here in Mexico on cuota toll roads and think it is a poor quality Pennsylvania interstate but even at half price it will add up. You will also experience little of the country.
Contrary to what has been posted above on this thread and some of the BS elsewhere on the HUBB, the real truth is that Gold Wings were never all that common in Mexico. Harleys became popular when taxation and imports changed under the Fox administration. BMW also opened up in a major way. Harleys and BMWs are the two largest touring brands in Mexico. I have known two Gold Wing owners here, big miles serious riders who did repairs locally and sourced parts via the US or a Guadalajara bike boneyard. You can find Gold Wings for sale, really old ones, most with dubious import papers, no papers, or imported as grey market.
Yes, you can tow the trailer but Sjoerd brings up some important points.
My bet is you will have more hassles from the trailer than the bike.
Buy yourself two good solid KLRs, put hard luggage on each, learn to ride them on the roads they were meant for and you will have the trip of a lifetime! Get an old Gold Wing with a trailer and miss the best parts of the various countries, pay bribes out the wazooo, get tired of answering the same questions while sticking out worse than you will on KLRs.
I have lived and ridden here full. time for 23 years and have yet to see a trip stopped on any bike by anyone short of accidents, of course. I know for a fact that at least in Mexico and Guatemala you can get anything fixed and parts within a week if you are willing to try.