Can I substitute fresh garlic for garlic powder? What's the ratio?

If you are making a creole seasoning as a pantry item, you should stick to dry. Otherwise you have a risk of spoilage. If it's for a dish you're about to cook, I assume you could go either way, according to your preference.

Seems like I will have to stock my pantry with the powder, then. ;)

You would be surprised how many creole recipes call for dry seasonings; garlic powder, onion powder, cayenne pepper etc. And not just for rubs.

Thank you, Hardlikearmour. I bookmarked the page.

http://www.foodsubs.com/Garlic.html