Hi!
I'm also having a hard time finding my mother and my aunt (which are still alive) in the 1940 Census. My mother was born and was living in Mayaguez in the 1940's.
I searched about 3 times before it was (INDEXED) line by line in all the different districts in Mayaguez and Cabo Rojo and I didn't find them. I searched again after it was indexed and I couldn't find them in the 1940 Census.
I just gave up! Maybe someone out there might be able to help.

Mildred