Měla byste mít drobné, když chcete platit v hotovosti.

It is the normal Czech way to express should have.

• mít = to have
• měla = the l-participle of mít, here agreeing with a female addressee
• byste = the conditional auxiliary used with vy

So měla byste mít literally works like you would have to have, but in natural English it is usually just you should have.

A very common Czech pattern is:

měl / měla / mělo / měli / měly + by + infinitive

Examples:

• Měl byste přijít dřív. = You should come earlier. (formal, man)
• Měla bys zavolat. = You should call. (informal, woman)

It is formal, and it is addressed to one woman.

You can tell because:

• byste and chcete are vy-forms
• měla shows the speaker is addressing a female

Compare:

• Měla byste mít... = formal, one woman
• Měl byste mít... = formal, one man
• Měla bys mít... = informal, one woman
• Měl bys mít... = informal, one man
• Měli byste mít... = several people / mixed group / men
• Měly byste mít... = several women

Because Czech often drops subject pronouns when the verb form already makes the subject clear.

Here, byste and chcete already show that the sentence is addressing vy. So writing vy is unnecessary unless you want extra emphasis or contrast.

For example:

• Chcete platit v hotovosti? = Do you want to pay in cash?
• Vy chcete platit v hotovosti? = You want to pay in cash?

The second version sounds more emphatic.

Because Czech marks gender in this kind of conditional construction.

• měl = masculine
• měla = feminine

So:

• Měl byste mít drobné = said to a man
• Měla byste mít drobné = said to a woman

This is something English does not do, so it often stands out to learners.

Here drobné means small change.

It is very commonly used when talking about money, especially in shops, cafés, ticket counters, or public transport.

Examples:

• Máte drobné? = Do you have change?
• Nemám drobné. = I don’t have any small change.
• Potřebuju drobné. = I need change.

Grammatically, drobné is an adjective being used on its own, with the noun understood. It is basically short for something like drobné peníze.

That is a very common learner question.

Když often means when, but in everyday Czech it can also mean if, especially in practical or general statements.

So in this sentence:

• když chcete platit v hotovosti
  means
• if you want to pay in cash

Other possible words are:

• jestli
• pokud
• jestliže

For example:

• Pokud chcete platit v hotovosti, měla byste mít drobné.

That sounds a bit more explicitly conditional, and sometimes a bit more formal.

Because Czech normally uses the present tense for general situations like this.

Když chcete platit v hotovosti means something like:

• if you want to pay in cash
• when you want to pay in cash

It is not talking about one specific future moment with a future-tense form. It is a general condition.

Also, chcete is the vy form of chtít = to want.

It means in cash, and it uses the preposition v with the locative case.

The noun is:

• hotovost = cash

After v, it becomes:

• v hotovosti

So:

• platit v hotovosti = to pay in cash

A very common alternative is:

• platit hotově

That also means to pay in cash. Both are natural.

Usually it sounds like advice, recommendation, or practical guidance rather than a strict command.

So it is closer to:

• You should have change than to:
• You must have change

If you wanted a stronger obligation, Czech might use muset:

• Musíte mít drobné. = You must / have to have change.

So měla byste mít is softer and more polite.

This is about aspect, which is very important in Czech.

• platit = imperfective
• zaplatit = perfective

In this sentence, platit is natural because the focus is on the method of payment in a general sense: paying in cash.

• když chcete platit v hotovosti = if you want to pay in cash

If you said:

• když chcete zaplatit v hotovosti

that could also be possible, but it sounds more like a specific completed payment. The imperfective platit is often preferred when talking about how one pays in general.

Yes. Czech word order is fairly flexible.

You can also say:

• Když chcete platit v hotovosti, měla byste mít drobné.

This means the same thing.

The difference is mainly in focus and style:

• Měla byste mít drobné... puts the advice first
• Když chcete platit v hotovosti... puts the condition first

Both are perfectly natural.