Theoretically, Pratyekabuddhas do not appear during a Buddha's
dispensations. They only appear during the gap between Buddha's
dispensations (e.g. the gap between Kassapa Buddha and Shakyamuni
Buddha)
As for during his times, Buddha said:
“In whatever Dispensation
there exists not the Noble Eightfold Path, neither is the first
Samana, nor the second, nor the third, nor the fourth, to be found
therein. In whatever Dispensation there
exists the Noble Eightfold Path, there are also to be found the
first Samana, the second Samana, the third Samana, and the fourth
Samana. In this Dispensation there exists the Noble Eightfold Path.
Here indeed, are found the first Samana, the second Samana, the
third Samana, and the fourth Samanas.
The other foreign schools
are empty of Samanas. If, O Subhadda, the disciples live rightly,
the world would not be void of Arahants.