I'd be putting up a lattice wall, next to the garage, with a few different clematis vines planted along the bottom. Shouldn't take too long before you'd be supporting the vines up to the lattice.I'd also be tempted to spray paint the lattice some earthy color, just for a splash until growth took over. Spray painting in sweeps would keep it from being a solid obvious paint job. Planters could be attached to the wall, too. I need something like this, to break up the not too cool view, from my kitchen window.

morning glories on a trellis can take an amazing amount of abuse, but it's only a half- year solution... well, maybe not in zone 7 : ) but I totally agree with strawberry that a vine on a lattice or trellis would be your fastest, easiest way ...or dig up a good chunk of soil, and put a climbing rose in there? I just moved into a house with 6 of them, and am totally enthralled, despite the bleeding I've done learning to deal with them.

Hot sun, poor soil--sounds like perennial morning glory territory to me! Also climbing nasturtium, scarlet runner bean, cup and saucer vine, or trumpet vine. While you're at it, even a poor string bean crop is better than nothing.
Don't bother with a trellis, just nail up a net.

preeva

Trumpet Vine will need LARGE support as it gets older. Honeysuckle smells awesome and after the second year shouldn't need any help covering your wall. I have one on lattice. If lattice is too expensive or you don't like the look of it I attached some heavy gauge picture hanging wire with screws at either end in a fan pattern to the brick side of my house and my climbing rose LOVES it there. Roses can take the heat as long as you keep them watered at the base.
Cris
Note: I am NOT a high-maintenance Rose gardener by any stretch of the imagination.

Sunflowers. At least they will give you time to plan for next year.