If you want if statement instead of signal, the closest you can get is use signal to turn some variable to true and then make condition to check that variable. When you press button, your if code will execute on next call of _process.
It could look like this:
get_node("Choice1").connect("pressed",get_node("Enemy"),"attack")
Then inside Enemy script:
var attacked = false
func attack():
attacked = true
func _process(delta):
if attacked:
attacked = false
#some other code...