Hello Tom, first I should say that Ruby is my favorite language and fortunately there is a lot of demand for Ruby development. I don't really pitch customers on language since almost everyone I work for is very tech saavy and know what they want they want to use.

If you want to work in a particular language such as Common Lisp I suggest writing a useful open source project and that could lead to work in Lisp, and at the least you will learn something and have fun.