There are about 2 million people who speak Esperanto. There are also Esperanto publishing houses, the largest of which are in China. A Chinese classmate of mine in graduate school had had a choice of only two foreign languages at her undergrad university in China in the 1980s – English and Esperanto.
In Michigan, there is even at least one native speaker of Esperanto. Native speakers of Esperanto exist generally because two Esperantists with no other language in common fell in love and got married (this usually starts with a penpal correspondence), and when they set up their household, they just continued speaking Esperanto.
You may think that’s weird, but remember that 100 years ago, there were no native speakers of Hebrew. Now there are not only native speakers, but you can easily identify someone with a Hebrew accent. There are quite a number of languages in the world that went or nearly went extinct and had to be artificially reconstructed. Hebrew is one of them, and the modern Czech language is also largely an artificial reconstruction.
The Esperanto language actually works quite well, and because it’s got no irregularities a person can learn it extremely quickly. I learned it as a sort of “experiment”, and I got the general grammar and vocabulary down to a useful level in only four days – I’m not the only one. I discovered later on that you can write or say as much in Esperanto as you can in any other language.
In my opinion, the only thing that’s stopped Esperanto from more general use – considering how easy and functional it is – is that Esperanto organizations are run by nuts who’ve attached an ideology to it. They run around saying that speaking a mutual language will lead to world peace. Well, the Iraqis and Kuwaitis, among many, many others, know this isn’t true. One president of the World Esperanto Association decades ago admitted that the language won’t succeed unless they somehow solve “the crank factor”.