Is Saliva an acid or base?
I can count four reasons that say saliva pH isn't the same among humans:


As people age, the composition of saliva changes in their body; this is easily explainable with the fact that the body isn't performing the actions the same way as you grow up or become old.
People have different eating habits; this will put the body in impression of producing especial kinds of enzymes and reduce\increase the production of certain factors in the saliva.
People aren't the same when it gets to taking care of the insides of their mouth. You can be brushing your teeth twice as much as a close friend of yours does.
Human digestive system isn't always performing its duties consistently and without "ups" and "downs" during the day, which has an important effect on enzymes produced.


And a sea of other reasons....

But, if we are to answer this question:


  Saliva is a watery substance located in the mouths of animals, secreted by the salivary glands. Human saliva is 99.5% water, while the other 0.5% consists of electrolytes, mucus, glycoproteins, enzymes, and antibacterial compounds such as secretory IgA and lysozyme. Saliva, wikipedia


I'll also say that according to here, a healthy range of pH of saliva varies between 6.5 and 7.5 during the day, but is optimally between 6.5 and 6.8.


Source

Thus, saliva is a very weak acid, or sometimes a very weak base. Considering something like that an acid or a base is like saying that the water we drink is a base and the water of the raindrops that fall from the sky of a peaceful country is acidic.

Saliva is really important for it's being a buffer.