I think you won't have a hard time finding either Ruby or Python programmers. Although, in general, I think it's better to just hire the best person and let them learn the language on the job. A decent programmer can pick up a relatively easy to learn language like Python quickly.
They are both very good languages, and you are unlikely to have "buyer's remorse" with either choice. Python is a little bit more mature, is better document, and has more libraries. People use it for web development, but they also just use it as a general purpose programming language. On the other hand, Ruby has some cool language features, and better support for functional programming. I notice Ruby doesn't seem to be used for much outside web programming. Python never has a problem with missing components. On the contrary, it has almost the opposite problem, in that there are many options to wade through when picking a library. There are usually at least 3 different implementations of everything in Python, and there are more web frameworks than I can keep track of. Probably Django is a reasonable default.
