Nah, screaming bluejays are not a dependable clue that they see deer.
They scream at almost anything.
There is a screech owl that lives in a hole in a tree right outside my bedroom. When bluejays and a few other birds see that owl at daybreak, all the screaming and racket starts and continues until the owl goes deeper into the hole.
Bluejays scream at fox, hawks, crows, housecats, red squirrels, and they even scream at each other.
Hearing the deer themselves...ground noise, grunt, wheeze, sneeze, bleat, antler clicks is the only dependable way to know a deer is coming.
I have seen movement of a sapling top (made by a buck rubbing it) long before I realized that there was a deer present.