Implicit type conversion is not an inherent property of dynamic typing. For example, Python does not do implicit type conversion except in arithmetic. You can't do, e.g., `4 + "hello"`.
Leaving that aside, though... I'm actually not convinced implicit type conversions are much of a win, especially when it comes to types other than the simple arithmetic ones (and those can often be handled in explicit type-checking anyway, through a numerical type hierarchy). I would rather be forced to handle explicit conversion everywhere I want it than accidentally forget about some edge case and end up with an unintended implicit conversion that causes unexpected behavior at run time.