Toria,
What is the leavening in your cake? If it were baking soda, then acid balance is present somewhere in the recipe to activate the baking soda. Baking powder has tartaric acid included to activate the baking soda in baking powder. Unless you are using egg whites or yeast for leavening, there will be some acid present in your recipe.
When I make pumpkin pie, I skip evaporated milk and substitute cream. I buy the Costco half gallon, so it is using something I have excess of and I like it.
I would simply use milk for the evaporated milk in your cake. Evaporated milk is often use for economy and for people who may not always have fresh milk available. There might be a change in the output, but I estimate there will be none discernable. If you made this recipe before and know how it should be, I would be interested in your thoughts on one made with milk.
Regards,