Hi Greg, thank you for joining our discussion.
In the Central Valley there are a few appraisers, there are also some home inspectors. I am not sure if they cover the whole country or specialize in a specific area. I think that it would be the same as for a realtor. An appraiser has to know the local market also and here the statistics aren't readily available from centralized sources. So you have to be in touch with the people who are actually closing deals and establish a level of trust with them in order to get the real information as to how much a certain property closed for in order to make accurate judgments as to the market value of another property.
All of the banks here have appraisers, called "peritos", so it is not a totally foreign concept and not illegal

Like many businesses, this is something that is common in other countries, that people moving here would be looking for, there is little or no competition, and something that you have experience in. So your chances for success should be very good.
Your best way of marketing would be working with and contacting reputable realtors in the area you are working in and letting them know about your services. They will introduce you to other reputable people and you could also advertise in the local English language papers for the area you want to specialize in.