Can window film let me see out without people seeing in?

Yes, during the day. A reflective film creates a one-way mirror effect: from outside people mostly see a reflection, while from inside you keep your view.

The effect depends on the light difference between inside and outside. The brighter it is outside, the stronger the effect. In the evening, when the inside is lit, it reverses. The more reflective the film, the stronger the mirror effect, and the more it reduces the light coming in.