Hmmm, maybe that depends on what you would consider a "wedding ring". The World of Disney in downtown Disney had a couple of different Mickey styles, most were cubic zirconia but I believe at least one of them was a diamond. The Contemporary resort and the Grand Floridian sell some jewlery but not sure how often their stock changes.
I can't think of anywhere that would engrave it though. If you just wanted the sentiment of buying the ring there, I'm sure an Orlando jewler or even your local one would perform that service for you!
Brenda