I mean, either you've agreed between you that you want to get married or you haven't. Tellling everyone that you're 'going to get engaged at Christmas' or that 'we're going to Paris to get engaged' doesn't really make sense. Surely its more exciting to wait until you have the ring and then make a general announcement that you 'are engaged' instead of letting everyone know in advance and then expecting them to get excited and ooh and aah when you appear with a diamond flashing on your finger.
I'm not giving out about it, I just don't understand why people want to take the excitement and surprise out of the occasion like this.