Looks good! You might want to try using a 1/2 to 3/4 inch thick layer of pearlite on top of your soil mulch-style. Its white color reflects most of the light energy that hits the dark soil and dries the top 1-3 inches out very rapidly. It also does a good job of locking in moisture in general and doesn't hamper watering efforts at all. As far as wall reflectivity goes, mylar is great but expensive. The name Mylar is owned by Dupont and makes it artificially pricey. Look up "metallized polyester" its the exact same stuff but about 1/3 the price. The little-known problem with both of these however is mold. You need to take mylar-style wall hangings down at least once per year and give them a good scrubbing, otherwise the moist, dark, warm little gap between the film and your wall will incubate all kinds of nasty stuff. Personally I don't find film methods worth the hassle, the best all-around solution IMHO is elastomeric paint. You can find it in the roofing section of any big box hardware store next to the various asphalt-based liquid tars (don't use these). Its cheap, (compared to mylar, kinda pricey compared to house paint) a very efficient reflector and best of all is highly resistant to molds and mildews. It'll last forever as long as you don't get it too dirty. Give it a try, I think it will impress you and even if you do end up going the mylar rout its mold-resistant properties should still help your cause.

Well here's an update. It's been around a month and a half. Most growth was probably between that pitaya and mango, but they were already germinated so it's not a fair comparison:
Opal Basil

mango:

pitaya:

lemon:

garlic (sorry for the bad quality):

cherimoya in the front, not really sure what's in the back, could be a weed:

papaya:

and last a passiflora that hadn't gotten watered in a week and got pretty dessicated: