Yellow is the color of spring for me, it jumps out and says winter is over! This shrub is my spring herald along with the daffodils. I have never heard a common name for it though there may be one in Mexico its home. In fact all I know it is a Senecio I bought from Yucca Do Nursery many years ago.
It will grow to 6' if you let it but looks better cut back to the ground every couple of years. In full summer sun it tends to wilt like a Hydrangea so be nice and plant it in the shade and hose it off on a hot day.
The Senecio is a coarse looking plant that fits well in a woodland setting but should be tried in a typical suburban landscape. It is an evergreen but not a dark dense plant. The branches are limber and the flowers sit at the ends. If I ever find the name I`ll pass it on!