I agree with the above post. In my opinion, the phrase, "Let's hit it!", by itself seems a bit awkward but things like;
"Let's hit the road!" (My Dad uses this often when we travel a long distance in cars. "Come on kids, it's time to hit the road")
"Let's hit the town tonight!"
"Let's hit up this ___(place)" (meaning, "go to, check out")
These all feel more natural.
On a side note:
"Hit (pronoun) up" can also be a very informal way to say "make contact with (via phone, email, message, etc)". I use it often though the same couldn't be said of my father...
For example,
A possible conversation with a friend.
Me: "Hey buddy, hit me up when you got a second."
Friend: "Alright, sounds good. I'll hit you up after I get off of work."