Question
I live in south Florida.  How often should I apply Weed 'n' Feed?  What time of year should I apply it?

Thank you.  

Answer
The best approach to take is "I want to get rid of the weeds". Bear in mind that St. Augustine grass and Bahia grass are significantly different in the way weed control should be tackled.
Generally, a weed killer is best applied:-
1. When the weeds are growing actively; in Florida there are two seasons of weed growth - "winter" and "spring".
2. When the weeds are young. For sure you want to get them before they flower and set seed. "One year seeding is ten years weeding".
3. As the last task in the cycle of cultural operations. Mow first, rake out junk, mow again if necessary, irrigate well (because you do not want to water again until you are quite sure that the active ingredient has been taken up by the weeds),then apply the product. Accuracy and coverage are the important watch-words.
Now as to the differences between the two lawn grasses:-
The chemical in the W&F for Bahia is often quite lethal to all broad leaf plants (this includes trees) so you need to be careful not to get it on or near to desirable bushes, shrubs and trees. Also watch the wind when you put down the product. And if you use this product on St. Augustine, you can kill the lawn. So please be careful.
The chemical used for weed control in St. Augustine turf is a "Restricted Use Pesticide" in some formulations but not in W&F products. However the potential for harm to the environment is still present. For this chemical, read the label 2 or 3 times and observe all the instructions. If it is applied on Bahia, it will kill the lawn. There is a saying among the professionals that;
     "Weed killers do not forgive!".
I cannot adequately stress the need for great care.