All,
I need to pipe a decorative ruffle border on a fondant covered cake. Can I use buttercream (will it stick?) or do I have to use RI?

B;cream should work just fine. It does depend on the recipe.......I always use what is often referred to as American b'cream

The only buttercream I have ever used was the Buttercream Dream recipe located here on CC. What's the difference between that and 'American Buttercream'? I'm not familiar...

I use BC for everything. Everything.

That is one of the many Amer. b'creams It works just fine.