It's both a 'yes'and 'no' answer here!
AIDS can, at least theoretically, be transferred by any body fluids so, obviously, this includes saliva. It's mainly for this reason that first-aiders are taught to use some kind of mask when giving the 'kiss of life' (although, of course, this helps protect against other diseases as well). Having said that, there have been hundreds of thousands of situations, throughout the world, where the kiss of life has been given without such protection and there has never been a recorded case of the infection being transferred by this means. Indeed, to the best of my knowledge, there has never been any recorded case of HIV being transferred by saliva but it still remains a theoretical possibilty.
Chris