3 ways I can think of
1/
have 4 areas that you can create in and choose one at random, these four areas will be something like (-300,-300 to 1380,0) (top area), (-300,0 to 0, 2220) (left area), etc
2/ create at (random( -300,1380),random(-300,2220))
check if the sprite is on screen
--if the sprite is on screen then destroy it and recreate it again at another random position
loop this until it isn't on screen.
3/ create at centre of screen
pick a random direction and face that direction
move forwards 1500 pixels
(I would probably go with 3)