dejaron una poesía no pocas veces admirable
I can translate most of the phrase, but I am having a hard time with "no pocas veces."
I'm not sure, but it seems to translate "no small times".
Considering the context, it could mean "not NOT often", meaning that the poem was often admirable.
The translator says it means "not infrequently", which would also work.
Basically, I believe this sentence is saying the poem was good or admirable.