dejar + saber
Dejar + saber does exist in Spanish in its proper context. (The Spanish language uses dejar + other verbs, but it takes issue with dejar + saber.)
Incorrect usage: Any expression with dejar saber is incorrect when
1) it is used in the imperative (command) form: D?jame saber si vienes. (Let me know if you are coming.) This is a literal translation of the English imperative let me know.
(Spanish uses hacer saber: Hazme saber si vienes. Or simply, Dime, av?same si vienes.)
2) it wants to convey the meaning of receiving knowledge, information from someone: Ella siempre me deja saber si viene a visitarnos. (She always lets me know if she is coming to visit us.)
(It should be: Ella me hace saber . . . Or me dice, me avisa, me informa.)
Correct usage:The English let also means to allow, to permit, and it is with this meaning that Spanish can correctly make literal translations, since dejar also means to allow: Ella me deja cuidar la casa. (She allows me to watch the house.)
Imagine a discussion between husband and wife when she tells him to go to bed but he wants to stay up and listen to the news:
Wife: Apaga la televisi?n y acu?state. (Turn off the TV and go to bed.)
Husband: D?jame saber si mi equipo gan?. (Allow me to know -to find out- if my team won, which also conveys the meaning, don’t stop me from finding out. (Although I would prefer to say, d?jame informarme.)
Dejar can be used as a helping verb with some infinitives: Ella se deja querer, She allows herself to be loved.
In the DR, se deja + certain verbs are used sarcastically: Se deja comer, indicates that the food is good; it allows itself to be eaten.