Please read my idea #27016 and consider that if the desktops are instantly available, with the current one in use a different colour to the rest, this would make life easier.
I still don't know why Unity "hides" these extra desktops instead of having these visible at the top of the screen, which would show users which desktop they are in and encourage users to make more space available on smaller screens e.g. netbooks with lots of programs open.