IMO, you must remove all of the existing shrubbery and replace it with things more promising. The existing shrubbery is wounded, downtrodden and has little chance of recovering. Plus, it was not chosen for low maintenance or excitement. Just start over. You stand a much better chance of making something good out of new plants ... planted a little farther from the wall so they have room to grow. A retaining wall is only necessary if you need to fix the grade for functional purposes, which doesn't seem to be the case. Instead, compensate for the falling grade by using a larger shrub at the low end and lesser height shrubs as the grade rises. In the area around the porch and farther left, you could get away with a single type of plant. (Any hedge that is part of a foundation planting should be trimmed level, not parallel to the grade ... so as to make the house appear stable.) Some color are around the entrance could help cheer up the overall scene. You really need to learn the proper way to trim shrubs as it will make an astounding difference. In order to keep the lower foliage, shrubs must be trimmed wider at the bottom then they are at the top. Of course, select varieties that can stand the existing light conditions as well.

I've avoided offering suggestions for a couple of reasons: first, because of the concrete borders you've already installed. My gut reaction is that if those spaces are planted in a typical way, instead of being an asset they would be a detriment to the overall appearance of the house and property. What compounds this and makes it worse is that one section of the walk is so darned skinny and the turn toward the house is so sharp! it cheapens the overall look of the house and should have been fixed before the borders were added. Second, while you've got a lot of pictures, the information they provide is limited, as the pictures are from all different points of view. What's missing is showing the whole scene from the most important -- front and center -- point of view. The second-from-last picture attempts to do this but it is incomplete and from too great a distance. Hate to be so picky about the pictures but they are what makes the property understandable to us and one of the best vehicles for us to convey suggestions back to you. I suppose the most probable fix is to do a foundation planting based on what the house needs (temporarily ignoring the bordered areas) and then plant primarily low groundcover in the bordered areas. (I would definitely consider perennial peanut for them since you are in Miami.) If you want help for how I think you should arrange a foundation planting, you would need to position the camera in line with the center of the house and midway between house and city sidewalk. It would stay in that position for all pictures, but pivot The series of pictures would span 180*. Begin by aiming far left, and finish aiming far right. We would see neighbor's properties at the beginning and end of the span, and your property at the center. If you look at some other threads, you will probably find examples of such pictures. They can be put back together to show the scene almost as if we were standing there seeing it for ourselves. Also, you might mention if you have any overall goals that are beyond the typical.

Judging by the (not-sunburned in full sun) archonotophoenix in the picture, I'm going to guess that if you're in the US, you're in coastal Southern California or coastal central California. The fence looks very modern. Is the house in keeping with that look also? If this space were mine to work with, I'd grow a bright red colored bougainvillea on the far right (San Diego Red or Purple Robe would really stand out against the white wall) and train it across the top of the fence. Then I'd use terra cotta pots and grow dramatic agaves like Agave attenuata, Agave blue flame or Agave desmettiana Joe Hoak. If my guess was correct and you are in fact in coastal California, the agave will not need irrigation. The bougainvillea might need water once a month once it's established.

In general, I think the house proportions would be improved by "stretching" the landscaping toward the left (when facing front door), and minimizing landscape along long wall of garage. So perhaps plant a japanese maple or large flowering shrub (e.g. rose of sharon, hydrangea, decorative grass, etc.) six to eight feet away from the corner of your house. That will "stretch" the house in that direction. Two alternatives for the remainder: 1) Along the long wall of the garage, add a window box planter, and just use stone for the bed itself. Add a flower box planter under window to the left of front door, and a trellis over the garage door with flowering vine. Or 2) Plant easy colorful plants (e.g. day lilies, or hostas, decorative grasses, etc.) along long wall of garage, and favorite flowering plants and shrubs in planting bed to left of front door.