50Hz yes, PWM no; well, not exactly.
The rate and duty cycles you mention will work, but the standard PWM pins don't run at 50Hz, more like 4 or 500Hz, which a standard R/C servo won't like.
Strictly speaking, R/C servos use Pulse Position Modulation (PPM), not Pulse Width Modulation (PWM).
The distinction is a fine one.