It is recommended that you replace the waterpump at the same time as the timing belt because it is in the same encloser and it would cost you double if you replace the waterpump then later have the timing belt go bad and have to replace that at a diffrent time. A lot of websites say to replace the timing belt at 60,000 miles. Here is one for you to see for yourself if you would like.
Although the California Owner's Manual says 105,000 miles, this is just to satisfy a state requirement that says timing belts should last 100,000 miles or more. Still, it should be done at 60,000 miles.