The StarCraft II beta is very much designed to be played against people. There is Artificial Intelligence you can choose to play against. However, Blizzard has perfectly simulated how a Ritalin driven child would play while being sedated and restricted to the use of only one finger.
They label this difficulty "Very Easy" and there are currently no others. I can think of very few friends of mine who, without ever having played StarCraft before, wouldn't be able to defeat one of these on their first try while blindfolded and forced to recite the Gettysburg address backwards. That's fine, it's labeled exactly what it is, but if you're an anti-social hermit the beta will not be for you.