I get absolutely nothing for this on Google. I checked the current topo map, and I find no Crystal Canyon in the area. Of course it's probably just a fanciful name the developer created. I looked at the 1947 and 1901 topo maps, and again I see nothing about that canyon or even any springs shown. There are a lot of tributaries feeding into the San Luis Rey River, so it's likely off of one of the smaller ones. The older maps barely show any buildings at all between Vista and Bonsall, even in '47.