Mexico is made for honeymoons. It brings together culture, history, beauty, luxury and of course those all important, spotless white sand beaches and gorgeous clear water. And, you can always pretend that you have eloped together over the border from the U.S like they do in films, which I am sure will add to the romance.
There are so many fantastic places to go and in every one of them is a classy hotel, set up for a romantic honeymoon. It is also perfect as only part of your honeymoon, with Central America, the Caribbean and the U.S all within easy striking distance. However, be careful if you decide to do this, I know from experience that Mexico is a very difficult place to leave.