The polish embassy website in Argentina specifically says that it takes about a month and half to submit the Pesel number once they ve been requested. However, I m still waiting for it even though I requested it 4 months ago.
Normal when applying for a PESEL through an embassy, I'm afraid.
It's worth noting that if you want to come to Poland, a temporary passport is enough - you'll have to get a Polish ID card once you come here, which is good enough for intra-EU travel.