Andiamo in prefettura piuttosto che dal giudice di pace.

Andiamo is the 1st person plural present of andare (to go).

So it can mean:

• we go
• we are going
• sometimes let’s go, depending on context and intonation

In this sentence, it most naturally means we’re going / we go.

Examples:

• Andiamo a casa. = We’re going home.
• Andiamo! = Let’s go!

Italian usually drops subject pronouns when they are not needed, because the verb ending already shows who the subject is.

• andiamo already tells you the subject is we
• so noi is optional

You could say:

• Noi andiamo in prefettura...

but it would usually add emphasis, as in we’re the ones going or as for us, we’re going.

With many places understood as institutions, offices, or services, Italian often uses in.

So:

• andare in prefettura
• andare in questura
• andare in banca

This often sounds like going to that office/service in its institutional function, not just to the building as a physical location.

Alla prefettura is also possible, but it tends to sound more like to the prefecture building/location.

So the difference is often:

• in prefettura = to the prefecture office / dealing with the institution
• alla prefettura = to the prefecture building/place

After in, certain place nouns often appear without an article, especially when they refer to common destinations or institutions.

So Italian commonly says:

• in prefettura
• in banca
• in chiesa
• in ufficio

This is just a normal usage pattern you have to get used to.

By contrast, with other structures you may see an article:

• alla prefettura
• nella prefettura
  depending on meaning

Here piuttosto che means rather than or instead of.

So the structure is:

• A piuttosto che B = A rather than B

In this sentence:

• in prefettura is the preferred option
• dal giudice di pace is the alternative being rejected

A very close equivalent would be invece che.

Not here.

In standard Italian, piuttosto che means rather than, expressing preference or contrast.

So here it clearly means:

• to the prefecture rather than to the justice of the peace

It is true that in some spoken Italian, especially in some regions and informal speech, piuttosto che is sometimes used like or in lists. For example:

• Possiamo andare lunedì, martedì, piuttosto che mercoledì.

But that use is often considered non-standard or at least something learners should be careful with.

For a learner, the safest rule is:

• treat piuttosto che as rather than

Because when you go to a person, especially a professional or official, Italian often uses da.

For example:

• vado dal medico = I’m going to the doctor
• andiamo dall’avvocato = we’re going to the lawyer
• vai dal dentista = you’re going to the dentist

So:

• dal giudice di pace = to the justice of the peace

Grammatically, dal = da + il.

Using al here would sound wrong in normal Italian if you mean going to see that person/official.

Because the two destinations are being viewed differently:

• in prefettura = going to an institution/office
• dal giudice di pace = going to a person/official

This is a very common pattern in Italian:

• in
  • office/institution/place
• da
  • person/professional

Compare:

• Vado in banca. = I’m going to the bank.
• Vado dal direttore. = I’m going to the director.

So the prepositions are not random: they reflect how Italian conceptualizes the destination.

Giudice di pace is a fixed job title / legal title.

• giudice = judge
• di pace = literally of peace

Together they form one expression: justice of the peace.

In the sentence, it appears after dal, which already includes the article:

• dal = da + il
• so the full idea is from/to the justice of the peace

The expression itself does not need another article inside it.

Yes, it can, depending on context.

Because andiamo can be:

• a normal present tense: we’re going / we go
• an exhortation: let’s go

Without more context, both are possible.

In actual use:

• with neutral intonation, it may simply describe a plan: We’re going to the prefecture rather than to the justice of the peace.
• with persuasive or decision-making context, it could mean: Let’s go to the prefecture rather than to the justice of the peace.

Context tells you which one is intended.

Yes. A very common alternative is invece di or invece che, depending on the structure.

For example:

• Andiamo in prefettura invece che dal giudice di pace.
• Andiamo in prefettura invece di andare dal giudice di pace.

These are very natural.

Roughly:

• piuttosto che = rather than
• invece che / invece di = instead of

In your sentence, piuttosto che is perfectly correct and natural.