Until you find the perfect vine, or until the perfect perennial vine fills in you could plant some sweet potato vine for this summer. Its really cheap and easy to find.

How tall is this wall? How far (down) do you want the trailing to go?

Creeping wire vine (Muehlenbeckia) will give you the effect you are looking for. I have some in a container going on 4 years, and it trails over the sides nicely. I have it in morning sun. What I don't know for sure is, if your sun situation would be too much for it. It is supposed to be marginally hardy here, (some sites list it as an annual) but so far mine has done well through DFW winters. 60' is a pretty long retaining wall. To keep anything from looking too blah, it might be a good idea to have several plants/vines at different parts along the wall to provide more interest. Depends on if it is a visible area or more of a background where blah would be fine as long as it's reliable and low maintenance.

Here is a link that might be useful: Creeping wire vine

The wall tapers from about 7' at the right side to ground level at the left side. It is basically one whole side of my backyard so I dont want it to be too blah. I'll look into the creeping wire vine, thanks. I'd like the trailing to go to the ground if possible.

I've got some Wandering Jew that will trail a bit -- so it might be better for the shorter portion of the wall. I just cleared out a bed, and I have several plants that you can have if you'll come pick it up.

~ freshair

My choices for this type of spot would be Purple Clematis (Clematis pitcheri) on the tall side transitioning to Winecup (Callirhoe involucrata) as the wall nears the ground.

Ty

Freshair - that would be great! Where are you located? You can email me at Justin.paradise@gmail.com. Thanks!

Irene rosemary or prostrate rosemary, Ornamental oregano like Kent beauty or any of the others.

As Freshair suggests, Wandering Jew (presumably Tradescantia pallida) isn't likely to trail very far. It's quite brittle. I'd be careful handling it, because it can cause skin irritation. I understand that, in times past, it was used to redden the cheeks (in lieu of pinching, I suppose.)

I once planted one of the suggestions, coral honeysuckle, alongside Japanese honeysuckle, and trained both up a trellis to cover the roof of a gazebo. Bonehead idea. When I became concerned that the weight of the vines was going to cause the roof to collapse, I stopped watering it. It didn't take long for the coral honeysuckle to gracefully expire, but its Japanese counterpart didn't even notice. Finally had to take Roundup to it. It's "invasive," of course, but I don't offhand see how it could do much damage in a confined area.