Aluminum bats do have "sweet spots", in fact they have bigger sweet spots than wooden bats.

A Sweet zone is the region located between the nodes of the first and second modes of vibration (between about 4-7 inches from the barrel end of a 30-inch Little League bat). Almost every bat on the market (especially newer aluminum bats) is claimed to have a "wider" sweet spot. Usually what such a claim means is that a certain bat is more forgiving for impacts outside of the sweet zone.

Here are some definitions of what is the Sweet Spot of a Baseball Bat, and how you can tell when you find it:
1.The location which produces least vibrational sensation (sting) in the batter's hands.
2.The location which produces maximum batted ball speed.
3.The location where maximum energy is transferred to the ball.
4.The location where coefficient of restitution is maximum.