[cflsystems]

I would create simple module, decorate View/CommonResources class

protected function getCommonFiles()

XC loads there "Open Sans" font from Google fonts and you can remove it and add Lato.
This has to be done with custom module - don't just modify the XC file.

You may need to modify some css files as well and replace every reference to "Open Sans" with "Lato"

OR you can also try with @font-face as this will create an alias for the "Open Sans"

@font-face {
font-family: "Open Sans";
src: url(/local/path/to/Lato);
}