El hotel está a trescientos metros de la playa, así que podemos ir andando.

Because Spanish normally uses estar to talk about location.

• El hotel está... = The hotel is located...
• ser would be used more for identity or essential characteristics:
  • Es un hotel pequeño = It is a small hotel
  • Está cerca de la playa = It is near the beach

So here, since we are saying where the hotel is, está is the natural choice.

In Spanish, estar a + distance + de is a very common way to express how far something is from somewhere.

So:

• Está a trescientos metros de la playa = It is three hundred metres from the beach

More examples:

• La estación está a dos kilómetros del centro
• Mi casa está a cinco minutos de aquí

This a does not mean exactly to here in English. It is just part of the Spanish pattern for expressing distance.

Because after a distance expression, Spanish uses de before the place you are measuring from.

• a trescientos metros de la playa
• a dos minutos del museo
• a una hora de Madrid

Also, la playa has the definite article because Spanish often uses articles more than English does with places and common nouns.

So even though English says from the beach, Spanish says de la playa.

Because metros is a masculine plural noun, so the number agrees with it.

• trescientos metros → masculine plural
• trescientas personas → feminine plural

This only matters for hundreds such as doscientos/doscientas, trescientos/trescientas, etc.

Since metro is masculine, trescientos is correct.

You usually need the subject unless it is already very clear from context.

Spanish often drops subject pronouns like yo, tú, nosotros, but it does not always drop other subjects like nouns.

So:

• El hotel está... sounds complete and natural.
• Está a trescientos metros de la playa could work if everyone already knows you are talking about the hotel.

In other words, omission is possible in context, but el hotel is the normal full version.

Así que means so, therefore, or as a result.

It links the first idea to the consequence:

• El hotel está a trescientos metros de la playa, así que podemos ir andando.
• The hotel is 300 metres from the beach, so we can go on foot.

It is very common in everyday speech.

Similar connectors include:

• por eso = for that reason / that’s why
• entonces = so / then
• por lo tanto = therefore (more formal)

Podemos means we can, while podríamos means we could.

Here, podemos sounds like a straightforward, real possibility:

• The hotel is very close, so we can walk

If you said podríamos ir andando, it would sound a bit more tentative or like a suggestion:

• we could walk

So both are possible, but podemos is more direct.

Ir andando means to go walking / to go on foot / to walk there.

It uses:

• ir = to go
• andando = the gerund of andar

Together, it expresses the way you go somewhere.

So:

• podemos ir andando = we can go on foot / we can walk there

It is a very common Spanish way to talk about travelling somewhere by walking.

Spanish can use both, but ir andando is especially natural when you mean go there by walking.

Compare:

• Podemos ir andando = We can go there on foot
• Podemos caminar = We can walk

Caminar focuses more on the action of walking itself. Ir andando focuses more on the means of getting somewhere.

In Spain especially, ir andando is extremely common in this kind of sentence.

Both can mean to walk, but there are some nuances.

• caminar = more directly to walk
• andar = can also mean to walk, but it is broader and often very common in everyday speech

Examples:

• Me gusta caminar por la playa = I like walking on the beach
• Voy andando al trabajo = I go to work on foot

In this sentence, andando sounds idiomatic because it goes well with ir.

Because así que introduces a result or consequence, and it is very common to separate that second clause with a comma.

• El hotel está a trescientos metros de la playa, así que podemos ir andando.

This is similar to English punctuation in a sentence like:

• The hotel is 300 metres from the beach, so we can walk.

In informal writing, punctuation can vary a bit, but the comma here is standard and helpful.

Yes. Está cerca de la playa means It is near the beach, and it is perfectly natural.

The difference is:

• está cerca de la playa = general idea
• está a trescientos metros de la playa = specific distance

So the original sentence is more precise.

The original sentence already sounds natural in Spain.

A few everyday alternatives could be:

• El hotel está a trescientos metros de la playa, así que podemos ir a pie.
• El hotel está muy cerca de la playa, así que podemos ir andando.
• Como el hotel está a trescientos metros de la playa, podemos ir andando.

Among these, ir andando is very common and natural in Spain, so your original sentence is absolutely fine.