Can we use other than the language of Arabic when we pray to Allah Almighty?
Well, there is no Noble Verse from the Noble Quran, nor there is any Saying (Hadith) from Prophet Muhammad peace be upon that directly say that praying to Allah Almighty has to be done with the Arabic language.
It is obvious that Prophet Muhammad taught us how to pray in Arabic, because that was the only language he spoke. And it is obvious that the Noble Quran was revealed also in Arabic. But to me, these are NOT good enough reasons or proofs to tell a new English-speaking Muslim convert for instance (such as an American, British or Australian) that he or she can not Islamically prostrate to Allah Almighty until they memorize few Noble Verses in Arabic so they can recite them in their prayers.
These new Muslims don't speak Arabic. To them, Arabic is nothing but babbling. It's like me reciting in Chinese. It will not mean anything to me, because I don't speak Chinese. This will disable the spiritual connection of the new non-Arabic Muslim convert with Allah Almighty. It is important to Allah that we have the spiritual connection with Him in our prayer. If we don't have it, then our prayer is worthless:
"Do ye enjoin right conduct on the people, and forget (to practise it) yourselves. And yet ye study the Scripture (i.e., the Noble Quran)? Will ye not understand? Nay, seek (Allah's) help with patient perseverance and prayer: It is indeed hard, except to those who bring a lowly spirit--Who bear in mind the certainty that they are to meet their Lord, and that they are to return to Him. (The Noble Quran, 2:44-46)" Notice here that Allah Almighty clearly says that prayer is hard except on those who have the spiritual connection with Him. So, unless the Muslim really knows what they are reciting in their prayers, there is no way they can establish that spiritual connection.
Allah Almighty doesn't care about our Physical prostration if it's not also spiritual: "The hypocrites--they think they are over-reaching Allah but He will over-reach them: When they stand up to Prayer, they stand without earnestness, to be seen of men, but little do they hold Allah in remembrance. (The Noble Quran, 4:142)" Notice here how the hypocrites for instance don't have that spiritual connection even if they physically prostrate to Allah Almighty.
"Recite what is sent of the Book by inspiration to thee, and establish regular Prayer: for Prayer restrains from shameful and unjust deeds; and remembrance of Allah is the greatest (thing in life) without doubt. And Allah knows the (deeds) that ye do. (The Noble Quran, 29:45)" How can prayer restrain someone from shameful and unjust deeds if he doesn't have the spiritual connection with Allah Almighty because his prayer doesn't make any sense to him what so ever when he performs it?
Certainly the hypocrites as shown above don't have the spiritual connection, even though they do sometimes prostrate. So it is not the physical prostration alone that Allah Almighty is looking for. How can a new non-Arabic speaking Muslim brother or sister have the spiritual connection when his/her prayer doesn't make any sense to him/her?
I am not in anyway trying to put our Muslim brothers and sisters who don't speak Arabic in the same categories as the hypocrites. No, that is not what I am trying to do here. I am just using the case of the hypocrites in the Noble Quran to help strengthen the case of our non-Arabic speaking Muslim brothers and sisters in Islam.
So my advise, or my opinion, or my verdict, whatever you wish to call it, is that a Muslim should try his best to prostrate to Allah Almighty. If he doesn't speak Arabic, then it is ok for him to recite the Noble Quran in his mother language and to perform the rest of the prayer also in his mother language, including Glorifying Allah Almighty and making wishes to Him, until he is able to master few Noble Verses in Arabic from the Noble Quran, and is able to memorize and appreciate the true Arabic meaning of the Glorifying of Allah Almighty and the making wishes parts. Until he is comfortable with that, he should stick with his language and perform the prayer in his language.
And Allah Almighty knows best.