Hi, I haven't been to Placenica for about 5 years, but will be there in November for a few nights. Check out www.seasprayhotel.com.
This hotel is centrally located, on the beach and I have heard good things about it. I recall that the airstrip in Placenica is not near any hotels and it is necessary to take a taxi into town.
For San Ignacio, I recommend Cahal Pech up on the hill above the town.
Have a great trip!