Many of the concepts in WCF and WF are language independent but it's hard to get a practical description of building services and workflows without making some assumptions about programming languages and tools. Much of the product documentation is available for both C# and VB developers. However, the typical article writer only provides examples using the predominant language for the product. I present everything using C# but I know that there are a large number of developers out there using Visual Basic. Recently I noticed that the Visual Basic MVPs had contributed some articles about WCF and WF to MSDN.
I've been seeing more articles and books lately that include VB as either a primary or alternate language when covering WCF and WF topics. I encourage these kinds of efforts to make content more broadly available.