Where is the ATM?
A more general and very common way to ask. It means 'Where is there a cash machine?' using 'hay' (there is/are) instead of asking for a specific one.
A casual way to ask, meaning 'Is there an ATM around here?'. 'Por aquí' is a very useful, high-frequency phrase.
A polite and slightly more advanced phrase: 'Do you know where I can get/withdraw money?'. Useful if the word 'cajero' slips your mind.
Excuse me, where is the nearest ATM?
Pardon me, do you know where there is a Bank of Bogota ATM?
I need cash. Is there an ATM around here?
Sir, where can I get money, please?
The full term 'cajero automático' is understood everywhere. However, in daily conversation, most people shorten it.
It's much more common to say just 'cajero'. For example, '¿Dónde hay un cajero?'.
'Cajero automático' or simply 'cajero' are both standard and very common.
'Cajero automático' is the standard term. You might also hear people refer to the specific network, like 'Servibanca'.
'Cajero' is common. Argentinians also frequently use the word 'plata' for 'money', so you might hear '¿Dónde puedo sacar plata?' (Where can I get cash?).
'Cajero automático' is used, but it's also very common to refer to the dominant ATM network, 'Redbanc'. Someone might ask, '¿Dónde hay un Redbanc?'.
Using 'es' instead of 'está'. For example, '¿Dónde es el cajero?' — Always use 'está' for location. 'Ser' ('es') is for permanent characteristics, not where something is located. The correct form is '¿Dónde está el cajero?'.
Mispronouncing the 'j' in 'cajero' like the 'j' in 'jungle'. — The Spanish 'j' (and 'g' before 'e' or 'i') sounds like the 'h' in 'hello', but made further back in the throat. Think 'kah-HEH-roh', not 'kah-JAI-roh'.
Forgetting the article 'el'. For example, '¿Dónde está cajero automático?' — In Spanish, you almost always need an article ('el' for masculine, 'la' for feminine) before a noun. The correct question is '¿Dónde está el cajero automático?'.