Carlitos made an album of his mother's pictures, and one such photo had the phone number of the house she was working at. Yet, he didn't take the phone number with him, even though he did take his mother's PO BOX address.
In the Beginning of the movie, Rosario is marking off a date which she has labeled "Carlito's Cumple" while she speaks in Spanish. There are no apostrophes preceding an "s" in Spanish, and the date should have read "Cumple de Carlitos".