Man, you've got a whole SLEW of things you need to take into consideration. First, you've picked a good tile. You definitely want a porcelain, so it'll stand up to the elements. However, you don't want to use the Ditra-Set to install the Ditra, unless you also get Hydroment's Flexalastic latex additive. Mix the Ditra-Set with straight additive, and no water for setting the Ditra, and then mix the Ditra-Set with water when you go to set the tile. One thing you need to be very sure of, and that is that the subfloor pitches sufficiently AWAY from the house. The pitch spec is the same as for shower floors-- 1/4" per running foot from the house to the edge of the deck. If you're going to have short walls going around the deck, you want to lap Kerdi-Band up the walls, and behind the finish as a kind of flashing to keep water from settling into the walls where it can freeze overnight during warm days and cold nights of spring. Also, if you have walls up around the porch, you want to have scuppers every so often where any water can drain off, instead of sitting on the tile and refreezing. Even with the Ditra, if water gets under the tile and freezes, it'll pop tiles. As for grout, Spectralock. That'll also help with keeping water out from under the tile, as well as standing up to the elements much better than a standard grout.

You can use cement mortar (thinset) for that application. You wouldn't want to use mastic, but thinset will be fine. Be sure and screw down the substrate material. Also since it'll be exposed to the elements it's a good idea to seal the grout joints.

Tile rainscreens have been used on commercial buildings in the US for many decades and for much longer in Europe and Southeast Asia but these systems have been far too expensive for the home market. What a rain screen does is increase the rate of moisture removal within a wall by creating a narrow continuous air space on the exterior side of the building weather barrier and on the interior side of the wall cladding. The wall cladding joints are not sealed and are open at the top and bottom. When tile is used as the cladding it hangs on a metal frame with lapped joints so there are no grout joints and the tile is self cleaning. These systems are usually proprietary and patented and they usually require factory trained and certified installers. Here are the details for the Laminam CS45D rain screen cladding system. (I believe the support systems are designed locally and the panels are from Italy) PLAN SECTION

Hi, Jenn-- Here in Southern California, red tile roofs are a pretty common occurrence, often used to invoke the Spanish Mission era settlements that first populated the area. Lots of great options here to work with the visual strength of a red tile expanse, but the one I find most successful is to work with the imagery of the original adobe and find inspiration there. The lighter (whiter) and brighter the stucco, the more it reads like whitewashed adobe, and a warm, medium to dark brown for the trim to resemble an unpainted wood tone. The combo really leavens out the intensity of the red and leaves you with a great framework that can feature a pop-of-color doorway in sage, turquoise, or ocean. You might also consider edging your front entryway in a red brick, or edging with Spanish tile to carry the theme through into the landscape--just a fun thought. Cheers!