I never learned Hebrew well, and though I pray in Hebrew, I feel much better praying in English. I am learning Hebrew, but I think it is best to pray in the language you understand best. God can translate, right?
Yes, it is allowed and okay to pray in English or any language that one understands. I suggest the ArtScroll Siddur's translation. However, since the prayers were composed in Hebrew by the 'Men of the Great Assembly' - and there were a number of prophets among them - there are special meanings and significance to the particular words of the prayers in Hebrew that will not be there in English, and it is preferred to pray in Hebrew if possible.
What I suggest is to pray in English, but persistently learn the prayers (and their meaning) in Hebrew, and then when you are able to pray in Hebrew you should switch over, one prayer at a time.
I hope this will help you and that God will answer all your prayers for the good.
