Congratulations and welcome to the forums! Your chance of rain here in Mexico is of course higher in Oct. Rains here tend to be shorter and heavier but more frequent in Oct. In the end, nobody will be able to tell you what will happen. You can have wet, dry, sunny, cloudy, cool, hot weather on ANY given day.
Biggest difference you can make... is to stay happy and positive on your wedding day and keep smiling. The rest won't matter!