One of the problems with waiting until the end of May to plant is that  the nurseries are frequently sold
out of the tomatoes you wish to plant.

Here's what works for me:

Plant the tomatoes around the end of April.
Surround them with "Walls of Water"
Get the heavy duty tomato cages, turn them upside down and place over the "Walls of Water"

The upside down cages keep the "Walls of Water" from blowing over during wind storms and help the walls
retain their shape.

Remove the  cages and walls around the end of May, turn the cages right-side up.

It is a good idea to loosely tie the plants in several spots to the cages while they toughen up out in the open.

Some years this gives us up to another month of fresh tomatoes.