Lascialo sapere! and Lasciatelo sapere! are Italian equivalents of the English phrase "Let it know!" Context makes clear whether one "you" (case 1) or two or more "you all" (example 2) suits. The respective pronunciations will be "LA-sha-lo sa-PEY-rey" in the singular and "la-SHA-tey-lo sa-PEY-rey" in the plural in Italian.
"Please let us know!" in English is Fatecelo sapere! in Italian.
"Let" in English is lasciare in Italian.
"Let's go!" in English means Andiamo! in Italian.
"Let's play!" in English means Giochiamo! in Italian.
lascimi avere
"Let's do it again soon!" in English means Ripetiamolo presto! in Italian.
"Let's go out to eat!" in English is Andiamo a mangiare fuori! in Italian.
lasciar andare
"Let's go to the beach Saturday!" in English is Andiamo alla spiaggia sabato! in Italian.
Parliamo italiano allora! in Italian means "Therefore, let's speak Italian!" in English.
Muoviamoci! is an Italian equivalent of the English phrase "Let's roll!" The declaration translates literally as "Let's move ourselves!" in English. The pronunciation will be "mwo-VYA-mo-tchee" in Pisan Italian.
"Talk to you tomorrow!" in English means Parliamo domani!("Let's talk tomorrow!") in Italian.