Does it sound natural?
It should be kept in mind that if you are a frequent visitor to restaurants, you should be ready to bump into some drawbacks of the food served there.

If not, how can I say it more naturally?

( I mean that restaurant food can be expensive or you can get food poisoning at restaurants.)

Question

Does it sound natural?
It should be kept in mind that if you are a frequent visitor to restaurants, you should be ready to bump into some drawbacks of the food served there.

If not, how can I say it more naturally?

( I mean that restaurant food can be expensive or you can get food poisoning at restaurants.)

Answer

"You should keep in mind that, if you are a frequent visitor to restaurants, you may experience  various shortcomings in the food served." or

"Frequent visitors to restaurants should keep in mind that they may experience various shortcomings in the food served."

I changed the initial passive clause to active, to match the later clause with "you" as the subject.

"there" at the end is not necessary.

Two clauses in the same sentence with "should" seemed excessive.

"drawback" is more "disadvantage" whereas here, you want to say that the food will sometimes be sub-standard.