Saltillo is a beautiful product but has some characterisitics very different from every-day ceramic and stone tile and requires a little extra effort in most cases.
True saltillo will be very irregular in the shape of each individual tile. Cupping and crowning will be the most obvious conditions. With saltillo, cupping and crowning is natural and an aspect of the beauty of the product but crowned tiles will require additional thinset under the tile centers to insure proper bonding and to eliminate voids that would compromise the support of the center of the tile. The same goes for cupping tiles but in this case the additional thinset and support is required along the edges of the tile.
Saltillo is very soft and pourous and should be well sealed prior to grouting. If the tiles are not pre-sealed then the grout will be very hard to clean from the surface and could leave streaks and haze that you won't be able to remove. Using a regular portland grout or even a modified portland grout will only add to the problem of cleaning unsealed tiles. Some installers prefer to use a sand-mix (portland and sand) for a grout and this product is a little easier to clean up than bagged grouts are. In many cases the cleanup difficulty comes from the color pigments that are added to colored grouts other than natural grey.
Sealing the tiles is highly recommended by this installer.