Long term, I've been thinking along similar lines, though more for a hybrid aesthetic-practical garden. The follow is for the Murcia/Almeria/Alicante area at low-altitude, from what I found out from some green fingered friends:
Citrus - Citrus trees do really well, obviously. In ultra-dry areas will need some water. They produce beautiful blossoms and you can usually get hybrid Orange-Lemon trees, which works nicely aesthetically and also means you won't be left with more lemons than you can realistically use.
Olives - Go without saying. Slow but very easy. Minimal maintinance, just make sure you get specimins that are already fruiting.
Dates - The Phoenix dactylifera "real" date palm does produce fruit in Spain, but is at the limit of it's range, so is less productive than it can be. Don't expect all fruit to ripen fully within the same period, etc. You can also harvest the fronds for making craftware, if desired.
Bananas - Keep out of the wind and water abundantly. They are within their thermal limits but the dryness is beyond their tolerance, so need good soil and abundant water to really get the best out of them. Won't be a productive as they are in their "real" climate, but the right varities will fruit nicely, and the leaves can be harvested too for presenting food.
Grape - Goes without saying. That said, they can be somewhat high maintinance.
Almond - Likewise. Has the benefit of being very low maintinance.
Mango - Yep, seriously. On the Med coastal plains you can make your own mango juice just fine :)
Avocado - Likewise does pretty well.
Lychee - Likewise
Kiwi - Does very well.
Pomegranite - Does very well.
Star Fruit (Carambola) - I love this fruit. My parents didn't grow it in Spain, but I'm inclined to think it should grow pretty well on the coast. It is grown in Texas and Florida in the US, which often experience cold snaps, and also in Israel which has similar climate to Spain, so I think it will work, and I'm looking forward to giving it a try one day.
Apples / Pears - In Murcia/Alicante/Almeria they are within range but beyond optimal range as they benefit from a sharper winter than the coast allows. They will fruit but don't expect the quality to be top notch.
Vegetables: Onions, peppers cabbages, tomatoes (not a vegetable but whatever!), taro andpotatoes are all good. Again you will need to water them in some regions. Tomatoes and onions in paticular grow very well in Spain. Taro isn't popular with westerners, but I'd reccomend giving it a try. It's a polynesian staple and it's popular with the locals in the Azores, so give it a try - needs plenty of water, but very tolerent of everything except severe cold. Almost all melons do very well.
Herbs/Spices: Lavender, saffron, mint, nettle, thyme, basil, oregano, coriander and bay all do well.
No-Nos - Coconut and durian are definitely out. They will not survive the winter anywhere on the mainland. I'm not sure about breadfruit, but the mainland is either beyond the limit, or on the extreme edge. I am not sure about
Hope this gives you some ideas for experimenting :)