They will also give you tips on how to deliver it, which is extremely useful whoever did the writing.
Few people are willing to trust everything to memory.
An alternative is to thoroughly familiarise yourself with your speech and then reduce it to a set of brief notes on cue cards. The advantage is that your speech will not sound as if it is being read word for word. But if you do decide to read it, nobody will mind. Whatever you decide - rehearse it. Then rehearse it again - until you are sick of it.