Well, from one designer to another...
It's a good thing to show a portfolio upfront to cut down on people wasting your time. From a consumer standpoint, it's difficult to say whether or not someone is serious about buying from you if they've never even saw your portfolio.
From a designer standpoint, people are gonna waste your time and not spend money regardless of whether they see a portfolio upfront or not. But it makes more sense to show one without them having to ask for it.