Although technically speaking the Halacha is that one may pray in English, the authorities emphasize the Halachic and spiritual advantages of praying in Hebrew and strongly discouraging using other languages. The Mishna Berura cites the Chatam Sofer and concludes that it is better to pray in Hebrew (Lashon HaKodesh) if possible, the words with which prayer was originally instituted.
Subsequently, if the person is able to read the Hebrew (not fluently) without understanding the meaning of each word, but with an understanding of each topic, it is preferable to do so. Both the ArtScroll Siddur and Machzorim (available on line from ArtScroll at www.artscroll.com and from any Jewish bookstore) are excellent as they have headings for each of the paragraphs of the Amida to make our prayers more significant. They also have extremely informative footnotes to both the prayers and the Torah Reading to enhance the "Prayer-Experience". It is important to know that praying with concentration and intent is something which takes work and does not come easily. But when a person finally becomes immersed in the prayers there is no other feeling like it in the world.
