Could taking baths in rusty water give me bladder cancer?

No. No current literature supports rusty water as a source of bladder cancer. If you can avoid bathing in rusty water, do:).
No. Bladder cancer is a multifactorial etiology. It is generally associated with smoking and certain carcinogens such as benzenes, dyes, etc. It can also occur without any risk factors, as with any cancer. However, it is not related to rusty water.