Learn Hardcore Spanish (Spain): Quedamos delante del restaurante por si acaso alguien se pierde. - We meet in front of the restaurant just in case someone gets lost.

In Spain, quedar means to arrange to meet. So quedamos = we meet/we’re meeting/let’s meet (context-dependent).
Quedarse means to stay. Nos quedamos = we stay.
Examples:
- Quedamos en la estación = we meet at the station.
- Nos quedamos en casa = we stay at home.

Why is the present quedamos used to talk about a future plan?

Spanish often uses the simple present for scheduled or planned future actions, especially in arrangements:

Quedamos mañana a las 7 is more natural than quedaremos in everyday speech.
You can also say vamos a quedar (we’re going to meet) or ¿Quedamos…? (shall we meet?).

Could I say quedemos to mean let’s meet?

Quedemos (present subjunctive) can function as a formal or emphatic suggestion: Quedemos delante del restaurante.
More common in speech are ¿Quedamos…?, Vamos a quedar…, or simply Quedamos… as a proposal.
Be careful: Quedémonos means let’s stay (here), not let’s meet.

What’s the difference between delante de, enfrente de, and frente a?

Delante de: in front of (near the front area, not necessarily facing or across from something).
Enfrente de / Frente a: opposite/across from, facing each other (often with some distance, like across the street).
In your sentence, delante de suggests gathering right in front of the restaurant, likely outside.

Why del and not de el?

De + el contracts to del: del restaurante. It’s mandatory.
With feminine nouns: de la (no contraction).
Do not confuse with de él (of him), which keeps the accent and does not contract.

Is adelante the same as delante?

Delante (de) is spatial: in front (of).
Adelante means forward/come in/go ahead, not a fixed location relative to an object.
- Pasa, adelante = come in.
- Delante del restaurante = in front of the restaurant.

How does por si differ from por si acaso?

Both mean just in case. Acaso adds a slightly stronger just-in-case flavor but is optional.
All are fine: por si, por si acaso, and colloquially por si las moscas.

Should it be subjunctive se pierda after por si (acaso)?

Standard usage is indicative: por si (acaso) alguien se pierde.
You sometimes see the imperfect subjunctive to mark a remote possibility: por si (acaso) alguien se perdiera, which sounds more tentative or formal/literary.
If you use en caso de que, then you need the subjunctive: en caso de que alguien se pierda.

Why not future se perderá after por si?

Spanish does not use the future in por si clauses. Use the present indicative:

Why is there no personal a before alguien?

The personal a is used with direct objects referring to people: Veo a alguien.
Here, alguien is the subject of se pierde, so no a.

Why perderse and not perder?

Can I change the word order or move por si (acaso) to the front?

Yes:

Do I need a comma before por si acaso?

Not when it comes after the main clause: Quedamos … por si acaso … (no comma).
If the por si clause comes first, use a comma after it: Por si acaso …, quedamos ….

Would en el restaurante or en la puerta del restaurante be better than delante del restaurante?

Delante del restaurante: outside, in front of the building.
En la puerta del restaurante: right at the doorway (very specific and common as a meeting spot).
En el restaurante: inside the restaurant. Choose based on where you actually want to meet.

Could I express the idea with para que?

Yes, but it slightly changes the nuance from precaution to purpose:

Quedamos delante del restaurante para que nadie se pierda (so that nobody gets lost). Here se pierda is subjunctive.
With por si (acaso), you’re preparing for a possible problem rather than stating a purpose.

Any regional notes?

In Spain, quedar (con alguien) is the default for arranging to meet. Alternatives you’ll hear: vernos, juntarnos, reunirnos (the last is more formal).
Por si (acaso) is universal.
Delante de, enfrente de, and frente a are understood everywhere; preferences vary a bit, but the spatial distinctions hold.