The course would be renovated around 1939 using WPA funds. Like the author of the article Jim linked to noted, there is no information out there as to who did this work.
Jan. 6, 1939 Miami Herald -
Is it possible Ross might have been involved somewhere along the way? Perhaps, but in 1922 and afterwards the Ross name held a great deal of cachet. If you had a Donald Ross course, you noted it.
Nothing out there mentions his name, nor did the great players who chose Sanford for many of their matches. All that was noted is that it was a good golf course.
There are a number of other factors that suggest this wasn't a project Ross would have had any interest in. First, it was initially to be a 9 hole course. In 1922 Ross was quoted he preferred not to work on 9 hole projects.
Second, the budget of this project was considerably less than those Ross normally took on, and it also seems like this wouldn't be a project where Ross could involve the construction arm of his business, which were most likely involved elsewhere in Florida at the time.
Finally, the timing of the project doesn't fit for how Ross worked. In 1922, he was booked out for months with a schedule that was probably set in stone. He had a trip to California planned for the summer, along with a number of other projects on the East Coast lined up for visits. The Sanford course had a very short period of time between conception and start of construction. The window for Ross being involved in the 1922 9 hole course starts on March 15, 1922 when Chase's brother suggested Ross by letter and ends in the middle of April when Cameron Trent was already moving dirt. And let us not forget that Chase was still conferring with William Langford about his possible involvement as late as March 27, 1922.
It would have been more likely that Ross was involved in the 1924 work or even possibly the 1939 renovation. But again, these are both activities that would have drawn the attention of the press.
As nice a story as it would be, it just doesn't make any sense. Neither does the idea that because they erected a plaque years later it means that Ross must have been there.