A question prompted by my son phoning from the UK to ask what the words were we say to our dog (always have spoken to animals in Spanish cos my mum always did from when I was little!!)
... so if you're in a Brit/Spanish household, which language do you use?
And if your animals are only ever spoken to in English, how do they react if a Spanish friend speaks to them in Spanish? (guess that's probably more about tone of voice than content, though!)

My dog appears to be bi-lingual, Spanish / English, however my guess is that intonation plays a big part.

Intonation is the most important part, you can use any word to make your dog sit, as long as you use the intonation you would use for 'sit', so you could say 'stand' but use the 'sit' intonaion and the dog will sit.

I would tend to agree about intonation, said it in my op, but when my son or daughter open the front door and tell the dog 'out' (and most people use the same kind of intonation for that message) she ignores them. I say 'fuera' & she's out straight away.

Our dog is Spanish but ingores everything you tell him in any language

Ours are multi lingual, understand anything you like as long as there is a sausage in it for them.
Actually I think they read minds, Spanish, English, French, German, Austrian, Swiss, no problems at all.

Have a biscuit in your hand and ours will follow you thru hell.

They understand food in any language.

If you start counting in German, when you reach 4 he'll start dripping, because it sounds like beer.

This is why ours is so disabidient , he`s not greedy so we cant bribe him

When you come to the number 6 in German, I hope your dogs are not of the same sex!

My dog is spanish and I use a mix of languages for her, I was told dogs here were trained in english as the sounds are shorter. I think she understands movement and hand signals better than voice.

Silly question, I mean

Who would teach a Spanish dog English?
Might be a business opportunity here though

Spaniards do, although only a few words such as "Sit" and "Stay"

As others have said, dogs rely on intonation which are clearly different in "Sit" and "Stay" but not so much in the Spanish equivalents "Siéntate" and "Quédate" (for example)

Much the same with mine as long as theres something in it for him.
Walk,food,scraps etc. no problem in three languages, however when it comes to direct orders he appears to be slightly hard of hearing.

I do very much get the impression he's a mind reader also, as he so often anticipates my activities and actions, even when I vary both the routine and timing.

Like you say, it's because dogs do better with simple single or double syllable commands. I was told that's why Italian police dogs are trained in German.

a good square kick up the ass, does away with the language problem, as dogs of all nationalities understand it...