Greetings, describing your holiday, signing off
A Spanish postcard has four short parts: a greeting, where you are, what you are doing / what it is like, and a sign-off.
¡Hola, Marta! (greeting)
Estoy en Valencia con mi familia. (where)
Hace sol y la playa es preciosa. (what it is like)
¡Hasta pronto! Un beso, Ana. (sign-off)
Postcards are informal — use warm openings and closings.
Open: ¡Hola, + name! · Querido Juan / Querida Ana (Dear...)
Close: Un beso · Un abrazo · Hasta pronto · Saludos desde Valencia
Querido agrees: querido Juan, querida Ana.
Location and feelings use estar; descriptions of the place use ser.
Estoy en Sevilla. (I am in Seville.) — location → estar
La ciudad es preciosa. (The city is beautiful.) — description → ser
Estamos muy contentos. (We are very happy.) — feeling → estar
Weather uses hace; current activities use estar + gerundio or the simple present.
Hace sol / calor / buen tiempo. (It is sunny / hot / nice weather.)
Estamos visitando la catedral. (We are visiting the cathedral.)
Mañana vamos a la playa. (Tomorrow we are going to the beach.)
Use the pretérito perfecto for what you have done so far on the trip.
Hemos visitado el museo. (We have visited the museum.)
He comido una paella riquísima. (I have eaten a delicious paella.)
Traps for English speakers
These are the errors English speakers make most often.