Pronouns – Is ‘Everyone’ Singular or Plural?

Some indeed can be use in this general sense.

If you visit OneLook, you'll see several meanings of the word some. One of them reads:

some used for referring to a person or thing without knowing or without saying exactly which one

So, saying:

We'll go to some beach tomorrow.

We'll stop at some restaurant on the way home.

are both perfectly acceptable. As a matter of fact, if you made the noun plural:

We'll stop at some restaurants on the way home.

That would imply that we are stopping at more than one restaurant.