I agree, but I don't see how the sign is forcing anyone to do anything. If the owner of a business wants to say adios to English speaking customers in hopes of attracting greater overall business from the Hispanic community, that sounds like good old capitalism 101. Go to eastern Los Angeles and you will see plenty of thriving businesses that made exactly that choice.
My other thought about this is that American kids should be taught Spanish along with other languages in elementary school. At least they would have learned something by the time they graduate.
Maybe it is just that I grew up in southern California, so Spanish signs seem normal to me.