In PBP, PORTC = %11111, for instance, will set RC0, RC1, RC2, RC3 and RC4.

This should be the same in your "0b11111" example. Since you do not care about RC5, and possibly RC6 and RC7, then you can use one of your three "PORTC = 0b111111" or "PORTC = 0b011111" or "0b11111" examples.

They will all set RC0, RC1, RC2, RC3 and RC4 anyway.