From everything I've read, while we need to remain hydrated, there are lots of ways to accomplish this, from drinking plain water, to juice, to tea, to the foods we eat (think about the water content in a lot of fruits and veggies, not to mention soup, as noted above). Apparently even caffeinated beverages, which are a diuretic, do not cause the kind of negative water loss that has often been hyped.
So, I think the short answer to your question is: yes.
In addition to keeping us hydrated, I think drinking water does sometimes help keep us feeling fuller, another plus for those of us trying to shed pounds.
My 5 C's of healthy living: Commitment to conscious control, with the understanding that choices have consequences