when's best time,folks say this month but if tree has flowers already have been told not to fertilize so any thoughts

Feb 15th, unless the tree has bloomed already. In that case I wait till the fruit is about the size of a dime or nickel and then do it...

What type of fruit tree?

Good point. I assumed citrus which is typically what would be fertilized this time of year.

yes citrus trees and also what about Avocados

I wouldn't fertilize anything this time of year. Especially if flowering. Best time to fertilize on most fruit crops is right after fruit drop. If you do fertilize use 0 percent nitrogen of low number. Micronutrients probably are more valuable for citrus. My lime bush is in full flower right now. I'm just watering it once a week. If you fertilize, gotta make sure to water it in good or it will burn the shallow roots in a drought. It's dry season now. I don't have a sprinkler system so my schedule is probably different.

The only thing I'm watering now is jaboticaba. They are in full flower.

Mango are in full bloom. I keep them dry this time of year. It's best that mango don't get any water during flowering.