HIV isn't transmissable (can't spell tonight, sorry) by saliva, only by blood, semen, vaginal secretions, and breast milk. Even if the spit got into the person's eyes, the chances of transmission are zero. Even *if* the person had fresh blood in their mouth when they spat, the chances of transmission would be virtually zero.
HIV is a pretty fragile, wimpy virus. It dies quickly on contact with air, and has to get into your blood stream for infection to occur. If you have no fresh cuts, scrapes, or abrasions on your skin, you could theoretically bathe in HIV positive blood and not get infected.
Still. Icky.