My boyfriend's Valentine's Day plans are ambiguous and I'm going to turn them down.
I know this is like asking the impossible, but can you clarify exactly what you mean about the plans being ambiguous?
There was no detailed info of where we were supposed to meet
Maybe his plans are ambiguous because he's trying to surprise you. It's wrong not to at least give him a chance to do that. He would be hurt.
I don't really like surprises. He should know that I don't like to be surprised by him.
Your partner probably put in effort to make these plans and it would be wrong to turn them down. Rather than not go, perhaps explain to him that you don't like the ambiguity and he will give you a bit more information.