TLDR: There's no benefit to drinking fluoridated water if you brush your teeth with fluoridated toothpaste (most toothpastes). There could even be potential harm, especially if you have hypothyroidism or are trying to have a baby.
I saw an article on fluoridated water recently, and thought to throw my hat in the ring to make sense of it for you all. There's a lot of controversy as to whether or not there should be fluoride in the water system.
-Fluoride works ON your teeth to prevent tooth decay, so drinking it doesn't do a whole lot for you unless you're swishing it around (http://www.ncbi.nlm.nih.gov/pubmed/19772849)
-Not only does it not do a lot for you, there is some research to show that fluoride accumulates in the body (not a good thing), and can affect thyroid function by blocking iodine uptake (which is critical if you want your thyroid to work properly). (http://www.medscape.com/viewarticle/840873)
-Decreasing your iodine levels is also not something you want if you're trying to have a baby (http://www.medscape.com/viewarticle/840056)
-If you brush your teeth with fluoridated toothpaste (most), you get enough fluoride in your regular toothpaste (http://www.ncbi.nlm.nih.gov/pubmed/21701195)
This is the most surprising point:
A lot of stuff to think about right?
All in all, there is very little to show that fluoride has any benefit now that toothpaste is fluoridated, and since the method action of fluoride is best when it's applied on the teeth rather than ingested, toothpaste is the best way to get your fluoride.
If you want to de-fluoridate your water, Reverse-Osmosis filtration is the most accessible and reliable way to remove the fluoride. Standard water filters like Brita don't remove fluoride.
Check to see if your community fluoridates it's water at this site: http://www.theregenesisproject.com/does-my-municipality-fluoridate-the-water/
Thanks for reading!