Agree with Gary

A 30 amp breaker should work fine. To answer your question, yes, the Baldor motor will pull 23 amps when the driven device (air compressor) is taking 5 HP. Inrush currents can be very high on startup, but most magnetic circuit breakers will handle it fine. If the compressor isn't using all 5 HP, current draw will be less.

Couple of things: make sure you get a breaker with a common internal trip (usually says so on the steel bar connecting the toggles). Also, circuit breakers aren't designed to be switches. I know too many people who use the circuit breaker to turn their air compressors on and off. Works in a pinch, but after too much abuse they'll either fail early or won't trip when they're supposed to. Either let the air compressor do the cycling, or get another form of disconnect between the breaker and the compressor. Magnetic starters (aka contactors) are the best way to go, but a cheap Square D nonfused disconnect works just fine too.

-Dave